You can only add or subtract monomials that have the same variable and the same exponent. For example, 2a + 4a = 6a and 4a² - a² = 3a² but 2a + 4b and 7a - 3b cannot be combined. However, you can multiply and divide monomials with unlike terms. For example, 2a x 6b = 12ab.

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

-3c + y = -3
y = -3 + 3c

then substitute the result (-3 - -3c) into the second equation:

-7c + 5(-3 + 3c) = 9
-7c + (5 x -3) + (5 x 3c) = 9
-7c - 15 + 15c = 9
-7c + 15c = 9 + 15
8c = 24
c = \( \frac{24}{8} \)
c = 3

To solve this equation, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

-9a(a - y)
-9(-1)(-1 - 7)
-9(-1)(-8)
(9)(-8)
-72

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the > sign and the answer on the other.

-2x - 2 > \( \frac{x}{-5} \)
-5 x (-2x - 2) > x
(-5 x -2x) + (-5 x -2) > x
10x + 10 > x
10x + 10 - x > 0
10x - x > -10
9x > -10
x > \( \frac{-10}{9} \)
x > -1\(\frac{1}{9}\)

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

-4a - 1 = \( \frac{a}{7} \)
7 x (-4a - 1) = a
(7 x -4a) + (7 x -1) = a
-28a - 7 = a
-28a - 7 - a = 0
-28a - a = 7
-29a = 7
a = \( \frac{7}{-29} \)
a = -\(\frac{7}{29}\)