You can put this solution on YOUR website! First of all 1.2 goes into 2.4 twice, so you can combine the z terms that way
2z-6.5=.7
Now add 6.5 to each side. 6.5 plus .7 is 7.2
so 2z=7.2
Divide each side by 2 to isolate the variable.
7.2 divided by 2 is 3.6
z=3.6