The freshman class treasury has 30 ten and twenty-dollar bills that have a total value of 430. How many of each bill do they have??
Let
x -----> number of ten dollar bills
y -----> number of twenty dollar bills
we have
x+y=30 -----> x=30-y -----> equation 1
and
10x+20y=430 -----> equation 2
solve the system
substitute equation 1 in equation 2
10(30-y)+20y=430
solve for y
300-10y+20y=430
10y=430-300
10y=130
y=13
Find the value of x
x=30-13
x=17
therefore
