I believe the formula to find the height would be h= 2a/b and if you use that formula and plug in the area (21.7) of each triangle as well as the base (6) then you would get a height of 7.2 cm. I hope this is correct! :)
The slope, if you have a graph, is the angle the line is going down so look at this graph:
<span>the rate of decay each month can calculated using the following formula:
</span><span>
6%/year × 1 year/(12 months) = 0.5%/month
0.06 x 1/12 = 0.005/month
</span><span>So the 0.5% is the right answer.
I hope it helped.</span>