Answer:
2.5
Explanation:
The equation will have infinite solutions when it is a tautology--when both sides say exactly the same thing.
Eliminate parentheses, match coefficients, and solve for b.
ax +ab = 4x +10
a = 4 . . . . . . coefficient of x
ab = 10 . . . . constant
Since we know a, we can find b:
4b = 10
b = 10/4 . . . . . . . divide by 4
b = 5/2 = 2.5 . . .express in your favorite form