how should i subtract two matrices

i need to subtrabt the first row B with the first number A

A=[ 6 12 15]

B=[50 70 80 90

20 50 40 30 % please note that vector B is a result of a for loop

10 60 80 90]

answer [44 64 74 84

8 38 28 18

-5 45 65 75]

Answer 1

[Alex Mcaulley]

A=[ 6 12  15];
B=[50  70   80 90;
      20  50  40  30;             
      10  60  80  90];
C = B-repmat(A',1,4);