Answer:
7
Step-by-step explanation:
get the x on the same side.
subtract 2x from both sides
30=3x+9
then get the variables on one side by themselves. subtract 9 from both sides.
21=3x
now divide by 3 on both sides.
there's your answer.
Answer:
4 x 3 x 1 = 12
12 = 12
Step-by-step explanation:
I used a calculator, pls let me know if im incorrect
Answer:
15
Step-by-step explanation:
Given the function

and 
let f(x)=y
Substitute in f(x)

From the definition inverse function
if
⇒ 
Substitute this in the above expression

Substitute y=10
⇒

Therefore a=15
Answer:

Step-by-step explanation:
we are given half-life of PO-210 and the initial mass
we want to figure out the remaining mass <u>after</u><u> </u><u>4</u><u>2</u><u>0</u><u> </u><u>days</u><u> </u>
in order to solve so we can consider the half-life formula given by

where:
- f(t) is the remaining quantity of a substance after time t has elapsed.
- a is the initial quantity of this substance.
- T is the half-life
since it halves every 140 days our T is 140 and t is 420. as the initial mass of the sample is 5 our a is 5
thus substitute:

reduce fraction:

By using calculator we acquire:

hence, the remaining sample after 420 days is 0.625 kg