Question

What are the answers and work for 15, 18, and 21

Answer 1

To solve equations such as the ones you listed above, our end goal is to isolate the variable (the letter that represents an unknown value).

Let’s begin with Number 15.

a/5 - 2 = 9

Due to the reverse order of operations, we should first add 2 to both sides of the equation.

a/5 = 11

To solve, we should multiply both sides by 5 to get rid of the denominator on the variable a.

a = 55 (answer)

Next, we can move onto number 18.

2/3g + 6 = -12

To solve this equation, we should begin by subtracting 6 from both sides.

2/3g = -18

Next, we can get the variable g alone by multiplying both sides by 3/2 (this will cancel out the coefficient of 2/3 on the variable g).

g = -27 (answer)

Finally, we can solve number 21 in a similar manner.

(c-5)/4 = 3

To solve this problem, we should first multiply both sides by 4 to get rid of the denominator on the variable c.

c - 5 = 12

To finish our simplification, we should add 5 to both sides of the equation to get the variable c completely alone.

c = 17 (answer)

Therefore, your answers to questions 15, 18, and 21, are 55, -27, and 17, respectively.

Hope this helps!

Answer 2

15) Here is the equation:

$\frac{a}{5} - 2 = 9$

Add 2 to both sides and it becomes:

$\frac{a}{5} = 11$

Switch that around and it becomes:

$11 \times 5 = a$

The sign changes. First you were dividing and now you're multiplying.

$11 \times 5 = 55$

a = 55

18) Here is the equation:

$\frac{2}{3} g + 6 = -12$

Subtract 6 and it becomes:

$\frac{2}{3} g = -18$

Divide by $\frac{2}{3}$ to leave the variable alone

$\frac{2}{3} g \div \frac{2}{3} = -18 \div \frac{2}{3} \\ -18 \div \frac{2}{3} = -18 \times \frac{3}{2} = -\frac{54}{2} = -27$

g = -27

21) Here is the equation:

$\frac{c-5}{4} = 3$

First multiply both sides by 4 to get rid of the denominator for c

$4 \times 3 = 12$

The remaining is -5. Switch it and it becomes +5. Add 5.

$12 + 5 = 17$

c = 17