Question 380386
Absolute value sign |x| is typed on a keyboard using "shift"+"\"

There are two cases for this problem:

5a + 7 = 6a - 7 --> a = 14

5a + 7 = -(6a - 7) --> 5a + 7 = -6a + 7 --> a = 0

Checking, both solutions satisfy the equation.