Since your total value on the card is $75, we will put that on the left of the equal sign. For our two variables, we will use x and y, following mathematical tradition. Let's assign x to the number of minutes spent calling the United Kingdom and y to the number of minutes calling France. Since it costs $0.23 per minute to call the United Kingdom, we multiply 0.23 by x and get 0.23x for the total cost to call the United Kingdom. Following the same idea, 0.21y will be the total cost to call France. Adding those terms together will give the total cost, so the sum of those two terms will go on the right of the equal sign. The finished equation is given below. 75 = 0.23x + 0.21y