#1
Let's simplify step-by-step.
−2(2a−b)+3(a+b)
=(−2)(2a)+(−2)(−b)+(3)(a)+(3)(b)
=−4a+2b+3a+3b
=−4a+2b+3a+3b
=(−4a+3a)+(2b+3b)
=−a+5b
#2
=(−5)(a)+(−5)(−2b)+(−5)(3c)+(−5)(−4d)+12a+−9b+6c+−3d
=−5a+10b+−15c+20d+12a+−9b+6c+−3d
=−5a+10b+−15c+20d+12a+−9b+6c+−3d
=(−5a+12a)+(10b+−9b)+(−15c+6c)+(20d+−3d)
=7a+b+−9c+17d