[section 6][combining like terms]

Combine like terms:

(1.)  3a + 2a + 4                here is the problem

=     5a + 4                        combine like terms

(2.)   8x + 3x + 9                 here is the problem

=     11x + 9                     combine like terms

(3.)  4a - b - 7b                 here is the problem

=      4a - 8b                     combine like terms

(4.)    2m + 7m - 8m               here is the problem

=        m                            combine like terms

(5.)   12x - 3y + x + 2y              here is the problem

=        13x - y                combine like terms

(6.)   8rt + 3rt + t - 3t           here is the problem

=     11rt - 2t                     combine like terms

(7.)  5x + 7x - 6y                 here is the problem

=      12x - 6y                      combine like terms

(8.)   4y - y + 8                      here is the problem

=      3y + 8                        combine like terms

(9.)    15 + 9y - 4y                   here is the problem

=     15 + 5y                         combine like terms

(10.)  19m - m - 3n + 2n               here is the problem

=      18m - n                   combine like terms