Solve ASAP for brain list and thanks make sure it's correct

The perimeter of a triangle is 69 cm. the first is 5 cm shorter than the second side. the third side is twice as long the first side. find the length of each side

That table shows measurements (in invhes$ from cubes with different side lengths. which pairs of variables have a linear relationship? check all that apply

What number is 7 units left of -15?