500 people go to a concert, X paid €35 and the rest (Y) paid €45. Total receipts were 20,500. Find X
Let x be the number that paid 35 pounds and y be those that paid 45 pounds
So we have this system of equations
x + y = 500
35x + 45y = 20500
And using the first equation, we can rearrange it as y = 500 - x....and subbing this in for y in the second equation, we have
35x + 45(500 - x) = 20500 simplify
35x + 22500 - 45x = 20500 combine like terms on the left side
-10x + 22500 = 20500 subtract 22500 from each side
-10x = -2000 divide both sides by -10
x = 200.....and this is the number of people who paid 35 pounds