Calculating Number of Students in Second Class: Average Score Statistics

[Femme_physics]

Homework Statement

Two classes made a test.
In one class there were 30 students, and the average score was 80.
In the second class, the average score was 70.
The average of both classes was 74.
How many students were tested in the other class?

Homework Equations

The solution is 45 students

The Attempt at a Solution

Attached. I'm getting a minus, clearly I'm off :/

Can anyone clue me in?

 

[danago]

You are dividing by 2, where instead it should be the total number of students in the combined classes i.e. 30+x

 

[Femme_physics]

Ah... I see the errors of my ways. Earlier I did 30x and got 1.11, I forgot that's not the total number of students..my bad. Thank you much.