Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 6 + 4 + 9 + 6
p = 25

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

y² + 8y + 15 = 0
(y + 3)(y + 5) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (y + 3) or (y + 5) must equal zero:

If (y + 3) = 0, y must equal -3
If (y + 5) = 0, y must equal -5

So the solution is that y = -3 or -5

The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 3 x 7) + (2 x 7 x 6) + (2 x 3 x 6)
sa = (42) + (84) + (36)
sa = 162

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

2a³ - 3a³ = -1a³

A cylinder is a solid figure with straight parallel sides and a circular or oval cross section with a radius (r) and a height (h). The volume of a cylinder is π r²h and the surface area is 2(π r²) + 2π rh.