Question 5703
You did good on distributing across the parentheses to get 4r - 8 = 2r + 16.


You tried to subtract 2 from both sides off the 4r and the 2r. However, this doesn't lower the 4r to 2r, or the 2r to r.


In Algebra, you can only add or subtract like terms. For now, a term is a single number by itself, a single variable by itself, or a combination of a single number (constant) and a letter (variable) multiplied together. "Like terms" means that the terms MUST be either all constants, or contain the same variable before you may combine them by addition or subtraction.


The attempt to say that 4r - 2 to equal 2r seems somewhat of a valid guess. However, since 4r and 2 don't have like terms (because one has a variable and the other doesn't), you can't combine the two by addition or subtraction.

In your case, your best bet would be to subtract 2r from both sides. Now you can say 4r - 2r = 2r because 4r and 2r are like terms.

{{{ 4r - 8 = 2r + 16 }}} <---- Started with this equation


{{{ 2r - 8 = 16 }}} <---- The goal is to "isolate" the variable as you know. Subtracting 2r from both sides gets rid of the 2r from the right side.


{{{ 2r = 24 }}} <----- We added 8 to both sides to get rid of the -8 on the left. (HINT: When we "move" terms from one side of the equation to another, we perform an opposite operation. The 8 was a negative, so we add 8 to "cancel the effect" BUT WE GOTTA DO IT TO BOTH SIDES. Earlier, we subtracted 2r from both sides (opposite operation of the +2r we began with).)


{{{ r = 12 }}} <----- Solve for r by dividing both sides by 2.