Question

Certain day in Bogotá, the temperature in the morning was 10 C or 50 F. At noon, the temperature was 15 C or 59 F according to this
What is the temperature in F if we know that the actual temperature is 20 C

Answer 1

Quick answer: 68oF <<<< 

A quick way to figure this out is to double the C temperature and add 30, just so you get an estimate. 
F ~ 2*20 + 30 ~ 70oF

Now let's use the actual formula
F = 9/5 * C + 32
F = 9/5 * 20 + 32
F = 180/5 + 32
F = 36 + 32
F = 68o

68oC <<<<< answer.