3x+20=100
Now you would need to move the constant to the right side and change within it’s sign
3x=100-20
Now you would subtract the numbers so for 100-20 would give you 80
So now you then do 3x=80
But if you want to divide the equation, divide it by both sides by 3
Which would give you x=80/3, x=26.6 or x=26 2/3