Question

I don’t understand at all

Answer 1

A=1/2ab
Replace the variables with their value
15=1/2(3/2)b
Multiply 1/2 and 3/2
$\frac{1}{2} \times \frac{3}{2 } = \frac{3}{4}$
15=3/4b
Divide 3/4 on both sides
15/(3/4) is the same thing as
$\frac{15}{1 } \times \frac{3}{4} = \frac{45}{4}$
45/4=b