Question

$a {}^{2} - b {}^{2} = 12 \\ a + b = 3 \\ a - b =$

Answer 1

a²-b²=12

a+b=3

(a-b)(a+b)=12⇒3(a-b)=12⇒a-b=12/3⇒a-b=4.

Bafta!

Answer 2

a² - b² = 12

a + b = 3

a² - b² = ( a - b ) ( a + b )

( a - b ) x 3 = 12

a - b = 12 : 3

a - b = 4