Question 548440
{{{m^2(m^3-y^3)}}}?
You could write that as m^2(m^3-y^3). (The caret symbol, "^" is used to show that what follows immediately after that is an exponent).
{{{m^2(m^3-y^3)=m^2*m^3-m^2*y^3=m^5-m^2y^3}}}
The first equal sign
{{{m^2(m^3-y^3)=m^2*m^3-m^2*y^3}}}
is applying the distributive property.
{{{m^2}}} is multiplied times the entire parenthesis, not just times {{{m^3}}}.
Imagine buying three units of an item that costs $9.95. The price per unit is ($10-$0.05). The cost of three of those is
3($10-$0.05)= 3($10)-3($0.05)=$29.85
If the cashier calculated your cost as
3($10)-$0.05=$29.95
you would complain, wouldn't you? 
The second equal sign
{{{m^2*m^3-m^2*y^3=m^5-m^2y^3}}}
uses the fact that when multiplying powers of the same base you get a power (of the same base) with an exponent equal to the sum of the exponents in the factors.
{{{m^2*m^3=(m*m*m)*(m*m)=m*m*m*m*m=m^5}}}