Question 217150
2^3 = 8

2^(2x - 1) = 2^3(x + 7)
2^(2x - 1) = 2^(3x + 21)

since the base is same , the index will be equal 
2x - 1 = 3x + 21
-1 - 21 = 3x - 2x
-22 = x