Question 206048
Let x = # of calls Tricia made and y = # of calls Michael made


Because "they made a total of 52 calls", this means that the sum of their calls will be 52. This means that {{{x+y=52}}}


Since "Tricia averaged 15 minutes" per call, this means that she talked a total of {{{15x}}} minutes (ie multiply the time per call by the number of calls to get the total). Likewise, since "Michael averaged 10 minutes" per call, we know that Michael consumed {{{10y}}} minutes total. Add these totals up and set them equal to the final tally 620 to get: {{{15x+10y=620}}}



So we now have the system of equations


{{{system(x+y=52,15x+10y=620)}}}



I'll let you solve for x and y. Let me know if you still need help.