4s/13+3/13=-1/13

Question

I am not understanding how this answer was got.  I need to see an explanation

Answer 1

4s/13 + 3/13 = -1/13 
13[4s/13 + 3/13 = -1/13] {multiplied entire equation by 13 to clear fractions}
13(4s/13) + 13(3/13) + 13(-1/13) {multiplied each term by 13}
4s + 3 = -1 {cancelled and multiplied what's left}
4s = -4 {subtracted 3 from both sides}
s = -1 {divided both sides by 4}
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