Given F = 120(2 ^ -at) + 60
use already given value to find a,
F=120 , t =10
120=120(2^ -a(10) )+60
60=120(2 ^ -10a)
solving we get a = 1/10

substitute for new value, F =75

Can you elaborate further...please..

Thanks..

You have to treat this as a function problem. It is really asking f(30) given the equation provided. For a function with an unknown value, here it is called "constant a," you have to first solve for the unknown value by plugging in the old value. In this case 10 for a and 120 for F, as the problem states. Once you figure out the unknown value, you plug in the known values, 1/10 for a and 30 for t. The rest is just arithmetic.