instruction:
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).
question:
Solve 23*o = 21*o - 4*u + 18, 4*o - 2*u + 14 = 0 for o.
answer:
-1


question:
15 + (7 + -17)/1
answer:
5


question:
Let r(n) = n**3 + 23*n**2 - 3*n - 49. What is the units digit of r(-23)?
answer:

0