Question

If $2x+y=23$ and $4x-y=19$; find the values of $x-3y$ and $5y-2x.$

Answer 1

2x+y = 23. .....(1)
4x-y = 19. ......(2)

Adding (1) and (2)
2x+y = 23
4x-y=19
-----------------
6x = 42
x = 7
Now Putting x=7 in (2)
4x-y=19
4$\times$7-y=19
28-y=19
y=28-19
y=9
So,
x-3y=7-3$\times$9 =7-27 = -20
x-3y=-20

Again,
5y-2x=5$\times$9-2$\times$7 =45-14 = 31
5y-2x = 31