a computer game and battery costs£21. the game costs £20 more than the battery.so how much does the battery cost?
let x be the game and y be the battery and we will solve them simultaneously:
therefore
we know that x=y+20
and y=21-x
y=21-(y+20)
=21-y-20
2y=1
y=1/2
if the battery cost 0.5 pounds, simply add 20 to find the games cost.
Answer= game = 20.5
battery = 0.5
total = 21