How to do the fourth and fifth questions on page 98 of grade seven in Mathematics People's Education Edition?

4. Set X ticket of Class A and Y ticket of Class B,

According to the meaning of the question:

{X+Y=35，…①

{24X+ 18Y=750，…②

Then ②: 4x+3y = 125...③,

①×3-③ Get: -X=-20，X=20，

Substitute X=20 into ① to get Y= 15.

5. (1) Equations:

{3X-Y=8……①

{3X-5Y=-20……②

①-②: 4Y=28，Y=7，

Substitute Y=7 into ①: 3x-7 = 8, X=5,

∴ The solution of the original equation is:

{X=5

{Y=7 .

(2) Transform the original equation into:

{8u+9v=6……①

{24u+25v= 14……②

①×3-②: 2v=4，v=2，

Substitute v=2 into ①: 8u+ 18 = 6 and u=-3/2.

{u=-3/2

{v=2 .