600 seconds would be 10 minutes, as there are 60 seconds in a minute.
Expressed as hours, that would be 1/6 of an hour.
Use order of operations
P
E
M
D
A
S
So multiply 5x6 to get 30
Then times 6x3 to get 18
Next times 4x9 to get 36
Add 30, 18, and 36 together to get
84
1.) a>10
2.) a<3.5
How I got it: 1.) Subtract 3 from both sides, leaving -2a<10.
2.) Divide by -2 from both sides, remember to flip the inequality sign when dealing with negatives. This leaves you with a>10.
For number 2.) I divided both sides by 5, leaving a<3.5, though this answer may be wrong.