Write an equation to find the value of x so that the polyhon has the same perimeter

Compare the subtraction problems 6/8 - 5/8 = 1/8 and 6/9 - 7/9 = 1/9 why is the answer to the first problem positive and the answer to the second problem negative

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'

Jordan got 27 out of 90 correct on his test . what fraction of the marks did her get correct