(can someone me) which of the following steps in this proof contains a flaw?

step 3 (incorrect multiplicative inverse)
step 4 (subtracted wrong expression)
step 5 (factored incorrectly)
step 6 (factored difference of two squares incorrectly)

How do i do this? i don’t understand

In a small section of a stadium there are 40 spectators watching a game between the cook islands and fiji. they all support at least one of the two teams. 25 spectators support the cook islands and 16 of these support both teams. how many support only fiji?

Given right triangle a w/a hypotenuse length of x+4 and a leg of x, and right triangle b, w/ a hypotense length of 3y and a leg length of y+4 for what values of x and y are the triangles congruent by hl?