Explanation:
scalar multiplication is simply done by multiplying every term of the matrix by the factor.
-1/5 A =
-5×-1/5 -15×-1/5 10×-1/5
-30×-1/5 20×-1/5 -25×-1/5
=
1 3 -2
6 -4 5
for the addition of 2 matrices imagine that each one is on a transparent slide, and you simply move both slides on top of each other, and you add all numbers for a position, that overlap each other for that position.
so,
-1/5 × A + B =
1+4 3+5 -2+ -7
6+7 -4+0 5+ -5
=
5 8 -9
13 -4 0