Just bought a home tutorial and the very firsr lesson speaks about commutative law which is confusing me.

Sample question was

100.21 + 23.42 + 2.79 - 13.40 =

using BEDMAS rule - we worked through the problem and came up with the answer 113.02

which the tutorial said was wrong.

The tutorial says we should add 100.21 + 2.79 (103) then subtract 23.42 - 13.40 (10.02) for an answer of 92.98 (based on this "commutative law"

what the heck???? is the tutorial correct? if so, can someone explain the concept to this confused middle-aged mom???

thanks