Question 842090
- find two equations in x and y, draw their graphs and solve graphically
q) In my pocket I have $1 and $2 coins. How many of each type do I have if I have 13 coins altogether and their total value is $20?
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x=qty of $1 coins
y=qty of $2 coins
x+y=13
x+2y=20
subtract
y=7
x=13-y=6
qty of $1 coins=6 (green line of graph)
qty of $2 coins=7 (red line of graph)

see graph below:
y=13-x
y=(20-x)/2

{{{ graph( 300, 300, -10, 10, -10, 10,13-x, (20-x)/2) }}}