(13s-8b)+(21a+9b)= (3×-17y+35z)+(4×+23y-9z)

(13a-8b)+(21a+9b)
=13a+21a-8b+9b
=34a+b

(3x-17y+35z)+(4x+23y-9z)
=3x+4x-17y+23y+35z-9z
=7x+6y+26z

maaf klo salah
#Charles