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

Answer: -5


Question: Suppose 0 = -5*d + 17 + 3. Let i(m) = m - 4. Let k be i(d). Suppose 5*w - 3*j = 14, 5*j - 2 = 2*w - k*w. Solve -w = -2*l + l for l.

Answer: 4


Question: Calculate prob of picking 4 x when four letters picked without replacement from {x: 5, u: 8}.

Answer:
1/143