(23+10)/2.75 = 12 is the answer
Answer:

Step-by-step explanation:
Given

Required
Determine an equivalent expression
In trigonometry:

In 

Substitute
for
in 


Hence, the equivalent expression is: 
Answer: 693 years
Step-by-step explanation:
Expression for rate law for first order kinetics is given by:

k = rate constant
t = time taken for decomposition = 1
= Initial amount of the reactant
= amount of the reactant left =



for half life : 

Putting in the values , we get


Thus half life of this isotope, to the nearest year is 693.
Answer:
x=9
Step-by-step explanation:
Use the intersecting chord theorem:
RE*ET = UE*ES
Substitute values
21 (2x+2) = 30 (x+5)
Expand:
42x+42 = 30x + 150
transpose and simplify
42x-30x = 150 - 42
12x = 108
x = 9