Problema Solution
Three friends put their money together to buy their favourite math teacher an end-of-year present. Jon put in $10 less than Andrew. Stuart put in twice as much as Jon. Together they put in $90. How much did each friend put in for the gift?
Answer provided by our tutors
let
j = the money that Jon puts
a = the money that Andrews puts
s = the money that Stuart puts
Jon put in $10 less than Andrew
j = a - 10
Stuart put in twice as much as Jon
s = 2j
together they put in $90
j + a + s = 90
by solving the system of equations
j = a - 10
s = 2j
j + a + s = 90
we find
j = $20
a = $30
s = $40
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