1/3+1/4=7/12 because changing the denominators to make them common gives you 4/12+3/12=7/12
Your average rate of change for the interval is 3/2 or 1.5, so that should be your answer.
3x + (x+3) = 19
4x + 3 = 19
4x = 16
x = 4
y= x+3
y= 4+3
y= 7
There are 10 portions to the circle, and 7 of the 10 are shaded. 7/10 is 70%