800 - 900 = -100. = 100/800=.125 x 100 = 12.5% increase.
Plug it in:
3x + 6(3) = 24
3x + 18 = 24
Then subtract both sides by 18:
3x + 18 - 18 = 24 - 18
3x = 6
Then, divide both sides by 3
3x/3 = 6/3
Simplify,
x = 2
Aⁿ means a times itself n times
a times itself 3 times means a³
There are a total of 3 zeros in this measurement that are significant.
D looks like the best answer