Rearrange the second equation: x=5y-18. Now we have two equations where x= an expression in y. We can therefore equate them: 10+y=5y-18. Now we have eliminated x and we just have an equation with one variable y, which can be solved: subtract y from each side: 10=4y-18; add 18 to each side: 28=4y; turn it round: 4y=28, and divide through by 4: y=7. We can find x by substituting this value of y in any of the equations where x= an expression in y. x=10+y=10+7=17; or x=5y-18=35-18=17.