Solve these simultaneous equations (2x+y=7 and 3x-y=8) and find the values of Equation: x and Equation: y .

-First of all add these two equations together so that the ys get eliminated. 
5x=15
x=3 
Since you have found the answer to x which is 3, substitute x into the equation 2x+y=7.
2*3+y=7
6+y=7
Therefore y=1 and x=3
Sometimes you will need to multiply one of the equations before you can add or subtract.