3(x - 4) = 15 help please?

Question

help me and stuck on all my questions so can somebody help me through my question

Answer 1

Remember that the number outside the brackets means that it is multiplied by whatever is in the brackets; also, we evaluate the part inside the brackets first, before multiplying. That is, if x = 10 we don't say 3(x-4) = 3*10 - 4 = 30 - 4 = 26; instead, we say 3(x-4) = 3*(10-4) = 3*6 = 18.

Now, 3(x - 4) = 15 and we want to isolate x. You can't break up a bracket that has something being done to it (like being multiplied by 3) - that's the whole essence of evaluating the bracket first. So we need to remove the 3 first. The opposite of multiplying by 3 is dividing by 3, so we need to divide both sides by 3.

3(x - 4) = 15 ==> (x - 4) = 15 / 3

Now the brackets are the outermost operation on the left, so we can get rid of them. Also, 15 / 3 = 5. So we get

==> x - 4 = 5

Now, we are subtracting 4 from x. The opposite operation is to add 4. So we add 4 to both sides:

==> x = 5 + 4
==> x = 9.