N=90 you have to simplify both sides then isolate the variable :)
3(x)-10=x+4. That’s the equation. Ight, now we gotta solve it. It would be 3x-10=x+4, then you subtract 4 from each side, so 3x-14=x, then subtract 3x, so -2x=-14, then divide -2x by -2 and -14 by 2, which means the answer is x=-7. Thank me later.
You are right ! It is 8.246 and so on ;)
They are essentially asking us to solve:

Solving this equation for x tells us that it will take around 80.1 years for the materials in the vault to reduce to 357 pounds.
Answer:
0.4494
Step-by-step explanation:
Given :
marks number of students
20-29 8
30-39 12
40-49 20
50-59 7
60-69 3
The range Coefficient is obtained thus :
Range Coefficient = (Xm - Xl) / (Xm + Xl)
Where ;
Xm = Mid value of highest class = (60+69)/2 = 64.5
Xl = Mid value of lowest class = (20+29)/2 = 24.5
Range Coefficient = (64.5 - 24.5) / (64.5 + 24.5)
Range Coefficient = 40 / 89 = 0.4494