I would say D midpoint! Hope this helps :)
Answer:
a= 135
Step-by-step explanation:
18*15=135
The first reaction represented is a decomposition reaction due to the fact the bonded pair are being split apart.
The second equation is a single displacement because the B and C have switched places, which is the only change making it a single displacement. If there had been another bond and A had also moved, it would be double.
We have,
Introduce variable 
such that 
The sum 
is therefore 
So,
(sadia's age)
(father's age)
Hope this helps :)
2.7? im actually not 100%sure on this one
