The equations would be:
x=18+3y
x+y=54
(substitute x in the second equation with 18+3y)
18+3y+y=54
(combine like terms and solve for y)
y=9
(plug y into the second equation to find x)
x+9=54
x=45
Y= 7x - 7z -9
+9 +9 Y+9+7z /7=x
Y+9 = 7x - 7z
+7z +7z
Y+9+7z = 7x
/7 /7
So (77 5/7)/17
5/7 = 0.7142
77.7142/17
=4.5714 rupees per metre
