设一本书x元,则小红带了(x-2.4)元,小华带了(x-4.5)元,小丽带了(x+0.5)元.
(x - 2.4)+(x - 4.5)+(x + 0.5)= 2x
3x- 6.4 = 2x
x = 6.4
∴x-2.4 =4
x+0.5 = 6.9
∴6.9 - 4 = 2.9
答:1本书6.4元,小丽比小红多带2.9元
设一本书x元,则小红带了(x-2.4)元,小华带了(x-4.5)元,小丽带了(x+0.5)元.
(x - 2.4)+(x - 4.5)+(x + 0.5)= 2x
3x- 6.4 = 2x
x = 6.4
∴x-2.4 =4
x+0.5 = 6.9
∴6.9 - 4 = 2.9
答:1本书6.4元,小丽比小红多带2.9元