Move all terms that don't contain K to the right side and solve.
K= Z/3 + 3
This is the answer for the calculation
The first equation is $3 times 9 = $27 the next equation iis $1 times 2 = $1
So you do 9 transactions over $100 and 2 transactions of $100 or lower.
x = -29
because
0.35x +1.4=0.25x-1.5
-0.25x -0.25x
_____________________
0.1x + 1.4 = -1.5
-1.4 -1.4
_________________________
0.1x =-2.9
____ _____
0.1 0.1
x = -29