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)]