If you would like to solve the equation 5 * a - 10 * b = 45, when b = 3, you can calculate this using the following steps:
b = 3
5 * a - 10 * b = 45
5 * a - 10 * 3 = 45
5 * a - 30 = 45
5 * a = 45 + 30
5 * a = 75 /5
a = 75 / 5
a = 15
Result: The value of a is 15.