(1) The sum of the prices of a basketball and a volleyball is: 42+28=70 yuan.
∴2 10÷70=3
Explain that you should buy three basketballs and three volleyball.
(2) If you buy a basketball, the remaining 2 10-42= 168 (yuan).
The quantity of volleyball to be purchased is: 168÷28=6 (pieces).
Then the total is 1+6=7 (pieces).
. . . . . .
So, everyone buys three.