Question 750136
First we write their total charges as equations. Then we solve for t - the number of hours when both charges are equal

{{{A=0.35t+25}}}


{{{B=0.50t+10}}}


When they charge the same A=B and we can write


{{{0.35t+25=0.50t+10}}}


{{{25-10=0.5t-0.35t}}}


{{{15=0.15t}}}




so t=100 hours



:)