This is a dilation transformation. As you can see the shape doesn't change: it just enlarges.
As a result of a dilation the dimension all get enlarged by a specific factor. This factor applies for all lengths.
That means we can find the factor by doing 60/3.75. Then we know this factor is the same one applied to the side length 2.5.
That means x = 2.5 * 60/3.75 = 40
