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

$70 spent altogether

Step-by-step explanation:

Since $20 is what Alex had left after spending 2/3 of the remainder, 20 must be 1/3 of the remainder, meaning the remainder would be 20 x 3, or $60 (and $40 was spent). As Alex had spent 1/3 of the pocket money and $60 was what was left after spending that, $60 must be 2/3 of the pocket money. We can divide 60 by 2, which gives $30, or 1/3 of the original as what he spent. $40 plus $30 is $70, so Alex spent $70 altogether.

I hope this helped! :)

assuming you mean addition: addition and subtraction are reverse operations.

step-by-step explanation: