3. -6x + 8 - 3x + 4y + 7x

This is combining like terms:

-6x - 3x + 7x = -2x

-2x + 4y + 8  

-2x +4y +8

Step-by-step explanation:

it will cost dollar $540

the living room is 3 which means if we divide 325/3 then we get $108

therefore if 1part of the living room cost $108 and 3 costed $325

then total 5part of the room will cost 5*108 which gives $540