Solve the simultaneous equations: 2x + y = 18, x - y = 6

There are two ways to solve simultaneous equations, by substitution or by addition/subtraction. The simplest solution in this case is a method of substitution:
Rearrange the simplest equation to get only x or only y on one side:x - y = 6 --> x = 6 + ySubstitute (6 + y) in for x in the second equation:2(6 + y) + y = 18Rearrange the equation to find the value of y:12 + 2y + y = 18 --> 12 + 3y = 18 --> 3y = 18 - 12 --> 3y = 6 --> y = 2Substitute this value of y back into the original equation:x - (2) = 6 --> x = 6 + 2 --> x = 8Answer: y = 2, x = 8