You multiply using the multiplication table. Multiplication is one of the four basic operations in arithmetic, along with addition, subtraction, and division. Multiplication can actually be considered repeated addition, and you can solve simple multiplication problems by adding repeatedly. For larger numbers, you'll want to do long multiplication, which breaks the process down into repeated simple multiplication and addition problems. You can also try a shortcut version of long multiplication by splitting the smaller number in the problem into tens and ones, but this works best when the smaller number is between 10 and 19.
what? um child.... anyways
You would graph the two lines. Then use Y=mX+b
10=5/4(4)+b 5/4 is the slope or distance between the two lines.
solve for b
10=5+b
-5
5=b
Y=5/4X+5 would be your answer
So hmm notice the picture below
thus, the perimeter of the gutter is just w + w + l, or 2w +l
thus

take the derivative of A(w), zero it out, check any critical points in the interval of (0, 22), for a maxima
recall, the aluminum sheet is just 22inches long, thus, whatever the "depth" or "w" is, has to be more than 0, and less than 22