Question

Solve the compound inequality 30 < 10u < 120

Answer 1

divide everything by 10 to get "u" all by itself

Answer 2

3< u <12; or in notations (3,12)

Answer 3

if you ever have to multiply or divide by a negative number; you need to reverse the signs.... thats the only caveat

Answer 4

for example:

we know that 5<8. if we multiply that by (2) we get:

10<18 which is a true statement.

but if we multiply by (-2) and dont flip the signs we get:

-10<-18 which is a false statement; in order to "correct" it we simply reverse the inequality symbol to "make" it true.

-10 > -18