Question

Over the last three evenings, Heather received a total of 107 phone calls at the call center. The first evening, she received 8 fewer calls than the second evening. The third evening, she received 3 times as many calls as the second evening. How many phone calls did she receive each evening?

Answer 1

x be number of phone calls received on first evening y be number of phone calls received on second evening z be number of phone calls received on third evening

x+y+z =100 -X&Y=8 2=34 2-3y=0

The coefficient determinant is D= The three determinants D1, D2 and D3 are obtained by replacing first, second and third column respectively of D 107 D1 = = 75 1 D2 = = 115 JO01 D3 = = 345 10 - 3 0 Hence x=D1/D = y= D2/D = z=D3/D = 69 Hence number of phone calls received on first evening = 15 number of phone calls received on second evening =23 number of phone calls received on third evening = 69