Question

There were 149 angelfish and goldfish in an aquarium.  There were twice as many guppies as angelfish.  After selling 35 goldfish there are half as many goldfish as angelfish.  How many fish are left in the aquarium?

Answer 1

$x- \ angelfish\\ y-\ goldfish\\ z-\ guppies\\\\ \left\{\begin{array}{l} x+y=149\\2x=z\\2(y-35)=x \end{array} \\\\ 2y-70+y=149\\ 3y-70=149\ \ |Add\ 70\\ 3y=219\ \ |:3\\y=73\\\\ x=149-73\\ x=76\\ z=2x\\ z=2*76=152\\\\ All\ fishes:\\ x+y+z=76+152+73=301\\ After\ selling\ 35\ goldfishes\ there\ are\ 266\ fishes\ in\ aquarium.$

Answer 2

149goldfish and 149angilfish Guppies Twice as many angilfish So 149angilfish × 2 ------------- 298guppies 298 +148 -------- 447total fish 447 - 35 --------- 414 left over