Ax 4 = e
b ÷ 4 = e
c + 4 = e
d - 4 = e

& a + b + c + d = 100

challenge
*what is the value of e ? *

E/4 + 4E + E-4 + E + 4=100
E/4 + 6E = 100
25E/4 = 100
E = 4.100/25
E = 4.4
E = 16

I hope it helps 

gregory's graph is incorrect because it shows 2 inches of growth for each week when it should show 0.75 inches of growth each week.

a² + b²= c²

24² + 7² = c²

c= 25