"Choose a number between 55 and 101 that is a multiple of 4, 7, and 14"

Both 56 and 84 are multiple of 4,7 and 14

Explanation:

Check if they're multiples of 7.

The multiples of 7 are: 56, 63, 70, 77, 84, 91, 98

Check if they're multiples of 4.

The multiples of 4 are: 56,60,64,68,72,76,80,84,88,92,96,100

Check if they're multiples of 14.

The multiples of 14: 56, 70, 84, 98

f(x) has value 150 at x= 0

and 0 at x= 3

so d(f(x))/dt = slope = -150/3 = -50