18a+-2a+-10a + -10b+12b+6b
just add/subtract the numbers with the same letters[18-2-10]a + [-10+12+6] b6a + 8b
we will separate the numbers18a+-2a+-10a-10b+12b+6bRULES: + with + = +- with - = ++ with - = -we will have 18a-2a-10a (we applied the last rule)=6a-10b+12b+6b= it's not wrong if we write12b-10b+6b=8bPutting all togheter, we will have6a+8b