(3.4a – 1.7b) + (2.5a – 3.9b)

Question

i just dont know how to solve this one

Answer 1

Take away the parentheses: 3.4a-1.7b+2.5a-3.9b.

Collect like terms together: 3.4a+2.5a-1.7b-3.9b.

Add the coefficients for each variable: 3.4+2.5=5.9 and -1.7-3.9=-5.6 and join the new coefficients to their variables:

5.9a-5.6b

Note that the variables are still separate: you can't join two unknowns.