The answer for the question is a
Why don't you first try to use the cosine law to solve for an angle and then make use of the sin law to solve for the remaining angles.
Cosine law
C^2 = A^2 + B^2 - 2AB(cos C)
Solve for cos C, and then take the inverse of the trig ratio to solve for the angle.
Then set up a proportion like you have done using the sin law and solve for another angle. Knowing the sum of all angles in a triangle add up to 180 degrees, we can easily solve for the remaining angle.
Exponential decay formula is :
Where a≠0, b≠1 , b represent growth or decay factor (or rate) and x is any real number.
But if a radioactive isotope decays in half every year which means the decay factor or decay rate is 50% or 
.
So, the formula for half decay will be:
Where represent c) The rate of isotope decreases.
Use a proportion.
2.2/5.5 = 48/x
2.2x = 5.5 * 48
2.2x = 264
x = 120
Answer: 120 ft
