Each day of overtime you work, you earn an additional $50 more than your regular pay of $100 a day.
if you worked overtime 3 out of 5 days this week, how much did you earn?

5 days normal
5*100=500
3 days overtime
3*50=150
total is 500+150=350

you earned $350

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.