How do I find the solution of the simultaneous equations x+3y=7 and 5x+2y=8

By looking at both equations you spot that the 'x' in the first equation has coefficient equal to 1, so it would be quite convenient to make 'x' the subject of the first equation and then substitute what 'x' is equal to in the second equation and multiply it by 5. So, x=7-3y therefore 5x=35-15y, and putting this term in the second equation we obtain 35-15y+2y=8, making 'y' the subject we obtain 13y=27 so y=27/13. Finally, substitute this value of 'y' in the first original equation and obtain the value of 'x'.