9/2 would be on the right -7/2 will be on the left hope i helped
4.2x - 1.4y = 2.1 |multiply both sides by 10
42x - 14y = 21 |subtract 42x from both sides
-14y = 21 - 42x |change signs
14y = 42x - 21 |divide both sides by 14
y = 3x - 1.5
If the two sides with length 3 and 4 are the two legs, then the missing side, i.e. the hypotenuse, is indeed 5.
But it could also be the case that 4 is the hypotenuse and 3 is one of the legs. In this case, the missing side is the other leg, so we calculate it using

So, a right triangle with legs
and 3 has an hypotenuse of 4.