The area of the rectangle is 1000 yd^2. To parallel sidesare fenced with aluminium at $15/yd one of the remanding side fenced with steel at $10/yd and all but 10 yd remanding side fenced with wood costing $5/yd. The reamding 10 yd of the remanding 10 yd are left unfenced . The total cost of the fencing is $1525
A.what is the length of the sided fence with steel?
b.what is the length of each side fenced with aluminium

Assign two variables to your sides.

Let y and x be the sides.

The area is given by xy = 1000
The perimeter is given by P = 2x + 2y

Two sides (let's assume x) are fenced with aluminium, hence, the cost for this is either 15(2x).
The remaining length to be fenced is 2y.
One of the sides is fenced with steel, and the cost will be 10y.

Subtracting the unfenced part, you know that the part fenced with wood is (y-10) which would cost 5(y-10)

The total cost is 30x + 10y + 5(y-10) = 1525

You have the equations:
xy = 1000
30x + 10y + 5(y-10) = 1525

Solve for x and y.

The part fenced with steel is y, and then part fenced with aluminium is x.