The space surrounding a charged object (source charge) is described as having an electric field. The electric field exerts an electrical influence on other objects that enter that space. The electric field value (E) provides a measure of how strong that influence is. The E value at any given location is dependent upon two factors - the quantity of charge (Q) on the source charge and the distance (R) that the location is from the center of the source charge.
 

Some problems in Physics don't involve plug-and-chug. They involve the use of an equation as a guide to thinking about how a change in one variable would affect other quantities. That's the case in this question. The variable that is different for these two locations is the quantity of charge on the Van de Graaff generator (Q vs. 3•Q). So you need to use an equation (better known as a relationship) to compare the electric field (E) for these two locations.



The Equation
The relationship between the Electric Field value (E), the separation distance (R) and the quantity of charge (Q) is given by the equation ...

E = k•Q/R²

where k is a proportionality constant.

The Application
From the equation, you would reason that the electric field value (E) is directly proportional to the quantity of charge (Q). So a larger Q value results in a larger E value. And 3 times the Q would result in 3 times the E value. So the location with the three times larger charge will have three times the E value.