The acceleration of an object is the ratio of the net force to mass. The net force can be determined by adding the individual forces as vectors. The as vectors clause here indicates that direction must be considered when adding the individual forces. When there are oppositely-directed forces, the smaller force must be subtracted from the larger force.
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You are presented with eight diagrams showing the individual forces on each object. You need to rank the eight objects in terms of their acceleration. This is a three-step problem. The first step is to determine the net force from the indicated force values. The second step is to use Newton's Second Law to calculate the acceleration. The third step is to do the rankings.

Determining Net Force:
 The net force experienced by an object is the collective effect of all the individual forces. Since force is a vector, direction must be considered. A leftward force subtracts from the effect of a larger rightward force and a rightward force subtracts from the effect of a larger leftward force. Forces directed in the same direction add together to produce the combined effect of a larger net force. So for oppositely-directed forces, you will have to subtract the smaller value from the larger value.  Forces in the same direction simply add together in the expected manner.

Determining Acceleration:
Newton's Second Law describes the relationship between acceleration and the two factors that effect it - mass and net force. In equation form, it can be stated as ...

a = F_net/m

where a is acceleration (in m/s/s), F_net is net force (in Newtons) and m is mass (in kg).

Once you have calculated the net force, take the ratio of net force to mass to determine the acceleration. Once all acceleration values have been determined, do your rankings. The most negative acceleration (caused by more left force than right force) receives the rank of 1; the second most negative acceleratione receives the rank of 2; and so forth. The most positive acceleration (meaning a rightward net force or more right force than left force) receives the rank of 8;  the second most positive acceleration receives the rank of 7; and so forth.
 

A Final Note

Because of the eight objects, there is a lot of work in this question ,,, and a lot remembering. And if you miss it, you will have to answer it correctly twice before earning the trophy for this Wizard Level. So here's something to think about: Sometimes the long cut is the short cut. Typically the short cut  is to do all the work in your head and to never write anything down. But if you miss the question because of a careless error in anyone of the eight diagrams, it's not much of a short cut. In this case, the short cut just might be to get out some scratch paper, make a 2x4 table and write some acceleration numbers down in each cell of the table before making rankings. It seems like the long cut but if it prevents you from having to answer the same question twice ... it's really the short cut.