Having this condition, you can IMMEDIATELY to conclude that 3 cases of juice cost 44 - 38 = 6 dollars. So one case of juice costs 6/3 = 2 dollars. To make this conclusion, you do not need to solve the system of equation. The common sense is enough. And the problems like this are designed to develop your common sense. Having this partial solution of $2 dollars per case of juice, you can complete the rest of the solution MENTALLY. Check yourself.