Let x be the cost of each juice and y be the cost of each BBQ.
4x + 2y = 16
4x + 3y = 21
Subtract the second equation from the first
y = 5
Substitute y = 5 into 4x + 2y = 16
4x + 2(5) = 16
4x + 10 = 16
4x = 16 - 10
4x = 6
x=1.5
Therefore, a juice cost $1.5 and a BBQ cost $5
So, if the Emdin family pu rchased 3 juice and 3 BBQ, then
cost of juice = 3 x $1.5 = $4.5
cost of BBQ = 3 x $5 = $15
Total money spent by Emdin family = $4.5 + $15 = $19.5
