All except combine like terms. Since you only have 1 variable.
Hope this helps.
r3t40
The answer is B. Infinitely many solutions. <span />
This might help it has tons of different problems for your subject.
https://www.wyzant.com/resources/lessons/math/algebra/calculators/proportion
The percentage increase; you'll need to take the new value and subtract it by the old value.
16 - 13 = 3
Next, you'll divide 3 by the original value.
3 ÷ 13 = 0.23
And multiply by 100
The percentage increase of friends is 23%