Identify the initial amount a and the growth factor b in the exponential function.
f(x) = 620 - 7.8^x

Step-by-step explanation:

An exponential function has the form:

y = a · b^x

Are you sure you copied the problem correctly?  Perhaps instead of minus, you meant multiplication:

f(x) = 620 · 7.8^x

If so, then a = 620 and b = 7.8.

144.50

step-by-step explanation:

21.5 x 13.4=288.10 divide by 2