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).

Ex Input:
Let u(n) = 5 + 3*n**3 - 4*n**3 + n + n - 3*n**2 + 7*n**2. Suppose 0 = -4*i - 2*t + 20, 3*i - 18 + 0 = -3*t. What is the units digit of u(i)?

Ex Output:
3


Ex Input:
Let z = 27 - 9. Suppose 2*t = -3*t - 4*l + 38, 4*l = 5*t - 22. What is the highest common divisor of z and t?

Ex Output:
6


Ex Input:
Solve 4*h - 4*d + 13 - 9 = 0, 5*h = -d - 5 for h.

Ex Output:

-1