To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

5a x 6b = (5 x 6) (a x b) = 30ab

You need to find the value of a so solve the first equation in terms of y:

a + y = -7
y = -7 - a

then substitute the result (-7 - 1a) into the second equation:

6a - 6(-7 - a) = 9
6a + (-6 x -7) + (-6 x -a) = 9
6a + 42 + 6a = 9
6a + 6a = 9 - 42
12a = -33
a = \( \frac{-33}{12} \)
a = -2\(\frac{3}{4}\)

A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².

A rectangle is a parallelogram containing four right angles. Opposite sides (a = c, b = d) are equal and the perimeter is the sum of the lengths of all sides (a + b + c + d) or, comonly, 2 x length x width. The area of a rectangle is length x width. A square is a rectangle with four equal length sides. The perimeter of a square is 4 x length of one side (4s) and the area is the length of one side squared (s²).