Step-by-step explanation:
remember the rules of exponents.
a "minus" sign means 1/...
like 2^-1 = 1/2
and 2^-3 = 2^(3(-1))
so, it is 1/2³ = 1/8.
so, now here in our case
y = 3×(1/2)^-2 = 3×(1/2)^(2(-1)) = 3×((1/2)²)^-1 = 3×(1/4)^-1 =
= 3× 1 / 1/4 = 3×4 = 12
