Answer:
3 fancy, 8 plain
Step-by-step explanation:
Let f be the number of fancy shirts bought
Let p be the number of plain shirts bought, then
f + p = 11 and
the cost of all fancy shirts bought is 20f (20 per shirt for f shirts) and
the cost of all plain shirts bought is 15p (15 per shirt for p shirts), so
180 = 20f + 15p (180 spent total on f fancy and p plain shirts)
system of equations
20f + 15p = 180
f + p = 11
solve second equation for f,
f = =11 - p
substitute this value for f into the first equation
20(11 - p) + 15p = 180, solve this for p
220 - 20p + 15p = 180, gather like terms
40 - 5p = 0, add 5p to both sides
40 = 5p, divide both sides by 5
p = 8, substitute this back into the second equation
f + 8 = 11, so
f = 3
