Let x equal the number
Tip: Go step-by-step
4 times a number is translated to... 4x
Is equal to means =
to the number increased by 21 is... x+21
Your equation is: 4x=x+21
Subtract x from both sides
3x=21
Divide three from both sides
x=7
Check!
4(7) = 7+21
28=28!
Correct!
Have a nice day!!