Ralph is in the business of constructing doghouses. A small doghouse requires 8 square feet (sq2) of plywood and 6 sq2 of insulation. A large doghouse requires 16 sq2 of plywood and 3 sq2 of insulation. Ralph has only 48 sq2 of plywood and 18 sq2 of insulation. Write the plywood constraint for the number of small doghouses (x) and large doghouses (y) that he can build with the available plywood.