Math problem confused!!!?

Question

4x+8=21

how can i possibly get an answer for x? im confused as to what the number would be. i cant figure it out. and if you do get me my answer can you please explain how you got the answer so i can do the rest of my work?? THANK YA!

OH,and this problem....

3y+2 over 4 =7

Answer 1

4x+8=21

subtract 8 from both sides 4x+8-8=21

4x=13 4x/4=13/4

divide both sides by 4

x=13/4 (3 1/4) or 3.25

3y+2 over 4=7

is that 2/4 or (3y+2) all over 4?

Answer 2

4x + 8 = 21 (subtract 8 from both sides to undo the addition)

4x + 8 - 8 = 21 - 8

4x = 13 (divide both sides by 4 to undo the multiplication)

4x/4 = 13/4

x = 13/4 <===ANSWER

(3y + 2)/4 = 7 (multiply both sides by 4 to undo the division)

4(3y + 2)/4 = 4(7)

3y + 2 = 28 (subtract 2 from both sides to undo the addition)

3y + 2 - 2 = 28 - 2

3y = 26 (divide both sides by 3 to undo the multiplication)

3y/3 = 26/3

y = 26/3 <===ANSWER

In order to isolate the variable on one side of the equation, you have to do the opposite operation of what is being applied. In other words, when there is addition, use its opposite subtraction, and when there is multiplication, use its opposite division, and vice versa when needed.

Answer 3

4x+8=21

4x=21-8

4x=13

x=12/4

x=3.25

Answer 4

ALWAYS: if you do something on one side of the equal sign, do the same thing on the other side

4x + 8 = 21

4x + 8 - 8 = 21 - 8  (subtract 8 from both sides)

4x = 13

4x / 4 = 13 / 4 (divide by 4 on both sides)

x = 13/4

3y + 2 / 4 = 7  (multiply both sides by 4)

3y + 2  = 28 (it cancels out the bottom on the left)

3y = 26 (subtract 2 from both sides)

y = 26/3