Sketch a diagram (dont draw 5625 squares just a rough sketch) and use an algebraic expression to find the number of squares in the border of a 75x75 grid.
can someone explain how to write the algebraic expression?

the 3rd option is right

step-by-step explanation:

43

step-by-step explanation:

this may not be at all, but i use the same website you're using for school, and if i'm stuck doing one of these i try to look for it on the section.

step-by-step explanation:

the ratio of red paint to blue paint is always 9/7. that means that, whatever x's value, (4x+12)/(4x-4) has that same ratio. so, set up an equation and cross-multiply to solve for x:

9/7 = (4x+12)/(4x-4)

9(4x-4) = 7(4x+12)

36x - 36 = 28x + 84

8x - 36 = 84

8x = 120

x = 15