Here two operations are involved #-# One, multiplication of #1xx4# matrics by a scalar and Two - addition of thetwo outputs.
When we have a #mxxn# matrics by a scalar, each element of the matrics is multiplied by that scalar resulting in another #mxxn# matrics.
Further when two matrices #A# and #B#, both #mxxn# are added, each element of the first is added to respective elememt of second to get respeective element of resulting matrics.
For example if #a_(mn)# is the #n^(th)# element in #m^(th)# row of #A# matrics and #b_(mn)# is similar element of matrics #B#, we have #c_(mn)=a_(mn)+b_(mn)#, where #c_(mn)# is the respective element of the sum of the matrices.
Here we have two #1xx4# matrices #[(0,-1,7,2)]# and #[(5,-8,10,-4)]# and hence
#5[(0,-1,7,2)]+3[(5,-8,10,-4)]#
= #[(5xx0,5xx(-1),5xx7,5xx2)]+[(3xx5,3xx(-8),3xx10,3xx(-4))]#
= #[(0,-5,35,10)]+[(15,-24,30,-12)]#
= #[(0+15,-5+(-24),35+30,10+(-12))]#
= #[(15,-29,65,-2)]#
