What is Seven more than twice a number is 11 find the number?

Answer 1

These kinds of problems are easily solved with simple algebra.

We let a letter symbol -- "n" for example, but it could by "x", "a", or whatever -- represent the number we're looking for, and then we construct a math sentence that is the equivalent of the verbal sentence expressing our problem.

Here we go:


"a number" turns into "n"


"What is" turns into "="


"seven more than twice a number" turns into "2n + 7"


The whole sentence is now:


11 = 2n + 7


Now we use very simple manipulations to isolate "n" on one side of the = sign.


First we get rid of the 7 by subtracting it from both sides of the = sign


11 - 7 = 2n + 7 - 7; that turns into 4 = 2n


Now we get rid of the 2 by dividing both sides by 2. This will isolate n, all by itself.


4/2 = 2n/2; that turns into 2 = n.


Wow! That's our answer: 2. Check this out: "Seven more than twice 2 is eleven". Is that true? Of course it is.