
That's 7.68% = 7.7% (rounded)
Note: C(5, 4) is the number of combinations of 5 things taken 4 at a time. You may have seen this written as

In general,
3x-4= - 10
add both side 4 so its a addition property
3x=- 6
now divide both side 3 so it is a <span>division property.
so x=-2</span>