Three classes of grade 6 donated money for "Hope Project". The donation amount of class 1 was 2 / 5 of the donation amount of the other two classes, and the donation amount of class 2 was 2 / 5 of the donation amount of the other two classes 3 / 7. It is known that class 3 donated 145 yuan. How much did the three classes donate?

Three classes of grade 6 donated money for "Hope Project". The donation amount of class 1 was 2 / 5 of the donation amount of the other two classes, and the donation amount of class 2 was 2 / 5 of the donation amount of the other two classes 3 / 7. It is known that class 3 donated 145 yuan. How much did the three classes donate?

The total amount donated by the first class: 2 (2 + 5) = 2 / 7
The total amount donated by class 2: 3 ÷ (3 + 7) = 3 / 10
The total donation of the three classes: 145 (1-2 / 7-3 / 10) = 350 (yuan)

For the hope project, grade 6 donated 240 yuan, of which class 6 (1) accounted for 1 / 4, and class 6 (1) donated 3 / 5 of class 6 (2). How much did class 6 (2) donate

240 - (240 * quarter + 240 * three fifths)
Equal to 240-60-144
It's 36 yuan

Four classes in Grade 6 of yanwai donated money for hope project. Class 1 donated 2 / 7 of the total, class 2 donated 1000 yuan, and class 3 donated 1000 yuan
Class three donated half of the sum of class one and class two, and class four donated 900 yuan. How much did the four classes donate

The total is x yuan
(X*2/7+1000)*(1+1/2)=X-900
3X/7+1500=X-900
4X/7=2400
X=4200
It's 4200 yuan altogether