Given a simple high-school level math question, you are required to solve it and provide the final answer. The final answer is always a single number. These questions can range from a variety of topics like simple arithmetic, solving equations, converting a quantity from one unit to another, finding remainders/GCD/LCM, finding probabilities etc. Each question has only one correct answer. This answer can be a positive or negative integer, a fraction or a decimal number. If the answer is a negative number use the hyphen (e.g. -42) symbol for the minus sign. For decimal numbers, do not add extra zeros after the decimal point. For fractional numbers, separate the numerator and denominator using a forward slash (e.g. 3/25).

Solve 4*f + 4*z = 0, 0 = -28*f + 29*f - 2*z + 15 for f.
-5

Calculate prob of sequence gyy when three letters picked without replacement from {g: 14, y: 4}.
7/204

In base 10, what is 2 - -137?

139