Question

2/3 times what equals 10?

Answer 1

You have to divide 10 by $\frac{2}{3}$

$\frac{10}{1}$ ÷ $\frac{2}{3}$ ⇒ $\frac{10}{1}$ x $\frac{3}{2}$

You use a method called "flip-flop and multiply" where you flip the second fraction to multiply 
$\frac{10}{1}$ × $\frac{3}{2}$ ⇒ $\frac{30}{2}$

Now divide the numerator (top) by the denominator (bottom)

$30$ ÷ $3=15$

Now lets check:

$\frac{2}{3} * \frac{15}{1} = \frac{30}{3}$

$30$ ÷ $3=10$ 

Answer: $\frac{2}{3}$ × $15=10$

Answer 2

Well 2/3=0.6666666666666666667  and 10/0,66...=15