Question

Alex spent 1/3 of his pocket money on a toy airplane and 2/3 of the remainder on a toy robot. He had $20 left. How much did he spend altogether?

Answer 1

He spent $70 in total! He spent ⅓ of his money on a toy plane remainder ³/³ -
⅓ = ⅔. Spent on toy robot = 2/3 * 2/3 = 4/9 
Total spent = 1/3 + 4/9 = 3/9 + 4/9 = 7/9 
Left = 9/9 - 7/9 = 2/9 
Then the final step, 
2/9 to $20 
1/9 to 20/2 = $10 
7/9 to 10*9 = $70

Answer 2

Answer with explanation:

Let Pocket  money Alex =$ x

Amount of money spent on toy Airplane $=\frac{x}{3}$

Money left with Alex

           $x-\frac{x}{3}=\frac{2x}{3}$

Amount of money spent on toy Robot

$=\frac{2x}{3}*\frac{2}{3}\\\\=\frac{4x}{9}$

Amount left after these two expenses=$ 20

Writing the above statement in equation form

 $\rightarrow \frac{x}{3}+\frac{4x}{9}+20=x\\\\\frac{7x}{9}+20=x\\\\x-\frac{7x}{9}=20\\\\\frac{2x}{9}=20\\\\x=\frac{180}{2}\\\\x=90$

So, Money spent by Alex =$90-$20

                      =$ 70