Question 244990
Of course, since there is no table included we can't complete it.
let w=white sweatshirts  and  r=red sweatshirts
30 sweatshirts were sold
r+s=30
s1895+r1950=57290
r=30-s
substitute 30-s for r
s*1895+(30-s)*1950=57290
s*1895+30*1950-s1950=57290
s*1895-s1950=57290-30*1950

Dig out the calculator.
30*1950=

57290-30*1950=

s1895-s1950=

Don't worry about the minus signs on both sides.
they go away by dividing
minus divided by minus= +