Can someone explain to me how to do this

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

Find the slope and the y-intercept if there's one and the equation of the line given these two points( 3, 2) and( 3, -4)

The square pyramid has a volume of 441 cubic inches. what is the value of x? 1/7x is the height x is the base