In science, variable values and constant values should not plugged into the equation until the equation has been rearranged to solve for the term of interest. When values are plugged in, they are accompanied by units. Units are added, subtracted, multiplied, and divided by each other exactly the same way youd add, subtract, multiply, and divide terms. The common units used in Chemistry are summarized in a separate document. A. 1 + 2 + 3x + 4x + 5x2 + 6x2 Only allowed to add or subtract like terms Therefore: 3 + 7x + 11x2 This is the same way wed treat units 5 cm + 3 cm + 12 cm3 = 8 cm + 12 cm3 Add the following terms 32a + 5b + 16a2 + 7b Add the following units 32in. + 5cm + 16cm2 + 7in. B. Whereas in multiplication and division, terms dont have to be alike to end up together or cancel each other (notice this problem includes both multiplication and adding!) 2x( 3 + 3x + 3x) = 6x + 6x + 6x This is the same with units 3 kg (5 m + 3kg) can be written as 15 kgm + 9kg 4 cm/5cm would be: 4 cmcmcm/5cm or 4 cm/5 or 0.8cm