Question

What is the value of x in the equation 3x – y = 18, when y = 27?

Answer 1

x = 15
explanation: 
3x - 27 = 18
3x = 18 + 27
3x = 45
  x = 45/3
  x = 15

Answer 2

$3x - y = 18 \\ 3x - 27 = 18 \\ 3x = 18 + 27 \\ 3x = 45 \\ x = \frac{45}{3} \\ x = 15$