In the cafeteria where I usually go to breakfast for coffee with milk and two toasts cost € 2. However, if I have a toast and two coffees with milk, the price is € 2.20.
Today I had a toast and a coffee with milk. How much did it cost me in total?
If we call T to toast and C to coffee with milk we have to:
C + 2T = € 2
2C + T = € 2.20
If we add both equations we have to:
3C + 3T = € 4.20
If we divide by both sides of the equation we have that:
C + T = € 1.4 which is the price of a coffee with milk and a toast.