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How to write the fourth question on page 55 of the second volume of seventh grade mathematics supplementary exercise?
Solution: Let each big cake be X yuan and each small cake be Y yuan.
2x+y=6
①
x+2y=4.5
②
Y=6-2x starts from ①.
③
Substitute ③ into ② to get x=2.5.
Substitute x=2.5 into ① to get y= 1.
So x=2.5.
y= 1
A: 2.5 yuan for each big cake and 1 yuan for each small cake.