3 t-shirts and 2 hats costs £14. 2 t-shirts and 7 hats costs £15.
Find the cost of a t-shirt.
Find the cost of a hat.
t-shirt: £
o
hat: £

Let the cost of t shirt be 'x' and hat be 'y'

3x + 2y = 14
3x = 14 - 2y
x = (14 - 2y)/3

2x + 7y = 15
2(14 - 2y)/3 + 7y = 15
28 - 4y + 21y = 15×3
28 + 17y = 45
17y = 45 - 28
17y = 17
y = 17/17
y = 1

x = (14 - 2×1)/3 = 12/3 = 4

Cost of one t-shirt = x = £4
Cost of one hat = y = £1

Is c^2-8c?
c^2-8c=c(c-8)