In two weeks, he has to do 24 chores because 2 x 12 = <<2*12=24>>24
He now does 28 chores a week because 7 x 4 = <<7*4=28>>28
He does 56 chores in two weeks because 2 x 28 = <<2*28=56>>56
He has done 32 extra chores because 56 - 24 = <<56-24=32>>32
He earns $64 because 2 x 32 = <<2*32=64>>64
#### 64