For any numbers a, b, and c,For which of the following equations is it true that there is exactly one positive integer that satisfies it’（）

单项选择题For how many positive integers m ≤ 100 is (m -5)(m -45) positive（）

A. 45
B. 50
C. 58
D. 59
E. 60

单项选择题If a is increased by 10% and b is decreased by 10%, the resulting numbers will be equal. What is the ratio of a to b（）

A.A
B.B
C.C
D.D
E.E