$1170
Given: 6kg rice costs $540
Find: cost of 13kg rice
13 kg rice x ($540 / 6 kg rice)
Units kg rice crosses out and you’re left with $ for units.
(13 x 540) / 6 = $1170
CHECK
13kg rice /6 kg rice = 2.17 bags to make 13kg rice
2.17 bags of 6 kg rice = $1170
So the answer is correct.
I suck at math but I got f(x)=(2x+3.5)^2-7.5
