Question

On Monday, Harold picked up four donuts and three large coffees for the office staff. He paid $4.96. On Tuesday, Melinda picked up six donuts and six large coffees for the office staff. She paid $8.70. What is the cost of one donut? what is the cost of one large coffee?

Answer 1

`x-cost\ of\ donut\\y-cost\ of\ coffee\\\\ \left \{ {4x+3y=4.96\ \ \atop {6x+6y=8.7}} \right. \\\\ \left \{ {{-8x-6y=-9.92} \atop {6x+6y=8.7}} \right.\\+-----\\\\-2x=-1.22\ \ \ |:-2\\x=0.61\\\\4\cdot0.61+3y=4.96 \\2.44+3y=4.96\\3y=4.96-2.44\\3y=2.52\\y=0.84\\\\Donut\ cost\ 0.61\ and\ coffee\ cost\ 0.84`