Question

Four pens and 3 erasers cost 17 . 4 erasers and 3 pens cost 18 find the total cost of a pen and a eraser

Answer 1

let pens be x and eraser be y
4x + 3y = 17 -(।)
3x + 4y = 18 ---(।।)
multiply first equation by 3 and second equation by 4 and subtract first from second.

Answer 2

let pen be x and eraser be y
so 4x+3y=17......1 eq
and 3x+4y=18………2eq
eliminating both eq we get
so y=3 and x=2