Question

Solve for x. x + 3x + 5 =21

Answer 1

Answer:

x=4

Step-by-step explanation:

In order to solve for x, we must isolate x on one side of the equation.

x+3x+5=21

First, combine like terms. x and 3x are both terms with variables, and can be combined.

(x+3x) + 5=21

4x + 5=21

5 is being added to 4x. The inverse of addition is subtraction. Subtract 5 from both sides of the equation.

4x+5-5= 21-5

4x= 16

x is being multiplied by 4. The inverse of multiplication is division. Divide both sides by 4.

4x/4=16/4

x= 16/4

x=4

Let's check our solution. Plug 4 in for x and solve.

x+3x+5=21

4+3(4)+5=21

4+12+5=21

16+5=21

21=21

This solution checks out, so we know our answer is correct.

x is equal to 4, x=4.

Answer 2

Answer:

x = 4

Step-by-step explanation:

x + 3x + 5 = 21

4x + 5 = 21

4x = 21 - 5

4x = 16

x = 16/4

x = 4

verify:

4 + 3*4 + 5 = 21

4 + 12 + 5 = 21