When we add 2 oranges and 5 oranges, we get 7 oranges. If we add 2 oranges and 5 pineapples you get 2 oranges+ pineapples. In algebra we can add or subtract like terms. Sum or difference will be another like term. 

Add: 6ab, -3ab, 4b, -b, -10ab

= 6ab-3ab-10ab+4b-b

= -7ab+3b

Subtract 4xy from -3xy

= -3xy-4xy= -7xy

  1. Simplify
 3x^2 y^2 + 4xy^2 -7xy^2-4x^2y^2= -x^2 - 3xy^2

2. Add 3x2 +y – z; 6x2 + 2z; 3z – 2y; and -3y + 2x2

(3x^2+6x^2+2x^2)+(y-2y-3y) + (-z+2z+3z)

=11x^2 - 4y + 4z

3. Subtract -2x2 y-2xy from 3x2y -4xy

3x^2y - 4xy - (-2x^2y - 2xy)=3x^2y-4xy+2x^2y +2xy

=5x2 y -2xy

4. Simplify

36 – [14a-3(8a-3)-4{9a-5(2-4a)}]=

=36 – [14a-24a+9-4{9a-10+20a}]

               =36 –[14a-24a+9-36a+40-80a]

                =36-[-126a+49]

                =36+126a-49

                = 126a-13