To solve for b, we need to isolate b on one side of the equation.
4a = 2b - 7
Add 7 to both sides of the equation:
4a + 7 = 2b
Divide both sides of the equation by 2:
(4a + 7) / 2 = b
Simplifying the right side:
2a + 7/2 = b
Now we can substitute a = 3 into the equation to find the value of b:
2(3) + 7/2 = b
6 + 7/2 = b
12/2 + 7/2 = b
19/2 = b
Therefore, the value of b when a = 3 is 19/2.