Gio mows lawns for $25 each. He already has $260 in his bank account, but is trying to save $900. How many lawns will he need to mow to reach his goal.
Gio needs to save $900, but already has $260, so he still needs to save $900 - $260 = $<<900-260=640>>640.
He charges $25 per lawn, so he needs to mow $640 / $25 = <<640/25=25.6>>25.6 lawns.
Since Gio cannot mow a fraction of a lawn, he will need to mow 26 lawns to reach his goal. Answer: \boxed{26}.