Simultaneous Equation Problem...

Jane wants to prepare a special diet for her pets. She requires a food mixture that contains, among other things, 29 ounces of protein and 6 ounces of fat. Food mixes are available with the compositions shown in the table. How many ounces of each mix should she use to prepare the diet mix?

In Mix A, there are 20% of protein and 2% of fat.

In Mix B, there are 10% of protein and 6% of fat.

I have no idea how to solve it but I know the answer is 114 ounces of Mix A and 62 ounces of Mix B. Thx.(Thinking)