From the question given;
5 = 2/5 m
25 = 2m
Divide both-side by 2
25 /2 = m
m = 25/2
Now to solve for H
( H + [ 1 4 -2 ] ) + [ 3 2 -6 ] = [-2 3 -1] + ( [1 4 -2] + [ 3 2 -6] )
( H + [ 4 6 - 8 ] )= [ -2 3 - 1] + [ 4 6 - 8 ]
( H + [ 4 6 - 8 ] = [ 2 9 -9 ]
Subtract [4 6 -8] from both-side
H = [ 2 9 -9 ] - [ 4 6 -8 ]
= [-2 3 - 1]
m x H = [ 25/2 * -2 25/2 * 3 25/2 * -1 ]
m x H = [ -25 75/2 -25/2 ]