Solution:
Given:

when a = 4, substitute for a in the expression;

Therefore, if (a = 4), then

Hence, the answer is 16.
All parabolas?
explanation:
Equation 1) 10x + 2y = 30
Equation 2) 4x + y = 4
Multiply all of equation 2 by 2.
2) 2(4x + y = 4)
2) 8x + 2y = 8
1) 10x + 2y = 30
Subtract equations from each other.
-2x = -22
Divide both sides by -2.
x = -22/-2
x = 11
B) x = 11
~Hope I helped!~