Answer:
$1210
Step-by-step explanation:
Let x be total amount
First John spent $110 on a radio and 4/11 of what was left on presents for his friends so he was left with
[tex]\frac{7}{11}(x-110)=\frac{7}{11}x-70[/tex]
Then he put 2/5 of his remaining money into a checking account
[tex]\frac{3}{5}\left(\frac{7}{11}x-70\right)[/tex]
Rest he donated to charity
[tex]420=\frac{3}{5}\left(\frac{7}{11}x-70\right)\\\Rightarrow \left(\frac{7}{11}x-70\right)=\frac{2100}{3}\\\Rightarrow \frac{7}{11}x-70=700\\\Rightarrow \frac{7}{11}x=770\\\Rightarrow x=1210[/tex]
Hence total amount of money John originally had was $1210