can you explain why how to get the "bold" one and why does it times by 3??

Question

3s² + 2t² = 11 — (1)

3s+ 2t = 1 — (2)

From (2)

3s = 1-2t

S = 1-2t/3

Substituting S = 1-2t/3 into (1) =

3(1-2t/3)² + 2t² = 11

(

1-2t)² + 6t² = 33

Answer 1

3(1-2t)²/9 + 2t²=11 ; the 3 that was in the denominator inside the parenthesis is squared giving 9 in the denominator (outside the parenthesis)

(1-2t)²/3 + 2t²=11 ; (3/9) reduces to 1/3

(1-2t)²+6t²=33 ; multiply every term on both sides of the equation by 3, i.e. clear the equation of fractions