He got $250 from his father
And the mother got 250$
It's like 500$
He bought the cell phone for $450
Harty paid 50$, zhpka paid 30$
it was 20$
His father gave him $10 and his mother gave him $10
Dad owes you $240 and Mom owes you $240
It adds up to 240 \$+240\$+30\$=510\$
The question is where did the 10 dollars go