Answer:
6 2/3 minutes
Step-by-step explanation:
Their rates in "jobs per hour" are ...
(60 min/h)/(15 min/job) = 4 jobs/h
and
(60 min/h)/(12 min/job) = 5 jobs/h
So, their combined rate is ...
(4 jobs/h) + (5 jobs/h) = 9 jobs/h
The time required (in minutes) is ...
(60 min/h)/(9 jobs/h) = (60/9) min = 6 2/3 min
Working together, it will take them 6 2/3 minutes.
Solve the following system using elimination:
{x - 2 y = -23 | (equation 1)
{x - y = 7 | (equation 2)
Subtract equation 1 from equation 2:
{x - 2 y = -23 | (equation 1)
{0 x+y = 30 | (equation 2)
Add 2 × (equation 2) to equation 1:
{x+0 y = 37 | (equation 1)
{0 x+y = 30 | (equation 2)
Collect results:
Answer: {x = 37 , y = 30
