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).

Example Input: Let i = -28 - -30. Suppose 4*z + 5*k = 200, -i*z + 81 = -k - 33. What is the tens digit of z?
Example Output: 5

Example Input: What is 51/2 of a millisecond in microseconds?
Example Output: 25500

Example Input: In base 14, what is -158 + 4?
Example Output:
-154