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 7 x 8) + (2 x 8 x 7) + (2 x 7 x 7)
sa = (112) + (112) + (98)
sa = 322

An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:

d° = b° + c°

To find angle c, remember that the sum of the interior angles of a triangle is 180°:

180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 40° - 47° = 93°

So, d° = 47° + 93° = 140°

A shortcut to get this answer is to remember that angles around a line add up to 180°:

a° + d° = 180°
d° = 180° - a°
d° = 180° - 40° = 140°

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.

(2a)(7ab) + (3a²)(9b)
(2 x 7)(a x a x b) + (3 x 9)(a² x b)
(14)(a¹⁺¹ x b) + (27)(a²b)
14a²b + 27a²b
41a²b

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.

3a - 7a = -4a

An acute angle measures less than 90°, a right angle measures 90°, and an obtuse angle measures more than 90°.