He is $45 short because 100 x .45 = <<100*.45=45>>45
He earned $55 off goldfish because 100 - 45 = <<100-45=55>>55
He makes $.5 profit per goldfish because .75 - .25 = <<.75-.25=.5>>.5
He sold 110 goldfish that week because 55 / .5 = <<55/.5=110>>110
#### 110