This is the commutative property of addition. It basically says, x+y=y+x.
To answer your question, 103+21=21+103
She has read 59% of the book so far, you simply divide and get a decimal which you round to
14)NO..... -2x+5y=10.....-2(-3)+5(2)=10.....6+10 is not =10
15)YES......-2x+5y=10....-2(-10)+5(-2)=10.....20-10=10
16)YES......-2x+5y=10.....-2(5)+5(4)=10......-10+20=10
$65 I believe because 6 times 15 is 90 and 90 divided by 36 (inches=yard) is 2.5 and 2.5 time $26 is $60