Math teacher doesn't explain this very well, solve.

a) Since we know they have equal perimeters, we can set them equal to each other. First, let's recap the perimeters of squares and triangles (s = side):


Now, we can set up our equation:



We can solve for x:




So, x = 10.

b) We known the perimeter formulas and we have what x is. So, let's just plug and chug.
Square:

So, the perimeter of the square is 28 units².
Since their perimeters are equal the perimeter of the triangle is also 28 units²