Answer:
3.6 hours
Step-by-step explanation:
To solve, create a Rate, Time, Work chart:
Work is rate times time. For Kevin, his work is going to equal x over 6 job. For Anna, her expression for work will equal x over 9 job.
The work is 1 job of calling all clients, so their combined work is equal to 1.
x over 6 plus x over 9 equals 1
In the rational equation, x is the amount of time it takes Kevin and Anna to call the clients together. With rational equations, the terms can be added together once they have common denominators.
x over 6 plus x over 9 equals 1
fraction numerator begin display style x left parenthesis 9 right parenthesis end style over denominator begin display style 6 left parenthesis 9 right parenthesis end style end fraction plus fraction numerator begin display style x left parenthesis 6 right parenthesis end style over denominator begin display style 9 left parenthesis 6 right parenthesis end style end fraction equals fraction numerator begin display style 1 left parenthesis 6 right parenthesis left parenthesis 9 right parenthesis end style over denominator left parenthesis 6 right parenthesis left parenthesis 9 right parenthesis end fraction
fraction numerator 9 x over denominator 54 end fraction plus fraction numerator 6 x over denominator 54 end fraction equals 54 over 54
9 x plus 6 x equals 54
15 x equals 54
x equals 3.6
If Kevin and Anna work together, they can call all the clients in 3.6 hours.
For question 3, you needn't worry about the number of total students asked. The question is really just asking you what's 45% as a fraction, which is 9/20. This is because 45% = 45/100, divided by 5 = 9/20.
For question 6, just substitute in the values. So you do 4(7 × 4 - 3 × -7), which gives you 4(28 - -21). Two minuses make a plus, so it's just asking you to do 4 × 49 (because 28 + 21 = 49). The answer is 196.
