First, understand that an exponential function is one that is of the form y = a*b^x + c
So, you have two points
For the first point: 7.5 = a*b^1 + c ==> a*b + c = 7.5 = 15/2
For the second: 16.875 = a*b ^3 + c ==> a*b^3 + c = 16.875 = 135/8
Notice that 2 = 2^1 and 8 = 2^3...
also 15 = 5 * 3^1 and 135 = 5 * 27 = 5*3^3
So, let's leave c =0 (to make the function less complex)
then a = 5, b = 3/2
so: y = 5 (3/2)^x
