Some children were riding on the bus. At the bus stop 2 more children got on the bus. Then there were 41 children altogether on the bus. How many children were riding on the bus before the bus stop?
Let's denote the number of children on the bus before the bus stop by x. Then the number of children on the bus after the bus stop is x+2. 

The total number of children on the bus is 

x+2+41=44. 

Therefore the answer (numeric) is: 

x+2 = 44-41 = 3


Q: In a class of 30 students, 18 passed the math test and 22 passed the English test. If a student passed both tests, how many students failed at least one test?

A: Let's think step by step. Introduce intermediate variables and solve the task symbolically. 

Let's denote the number of students who passed the math test by x, the number of students who passed the English test by y, and the number of students who failed at least one test by z. 

Then we have the following system of equations: 

x+y=30 

x=18 

y=22 

x+z=18 

y+z=22 

From the first equation we get that 

y=30-x. 