The sum of a number and 3 times a second number is represented by a+3b=39. the sum of half of the first number and 1/3 of the second number is represented by 12a+13b=9.
what is the first number (a)?
a =
what is the second number (b)?
b =
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 The first number is a = 12 and the second number is b = 9.

Step-by-step explanation:  Given that the first number a and second number b is related to each other by the following system of equations :

We are to find the first and second number, i.e., a and b.

From equation (i), we have

Substituting the value of a from equation (iii) in equation (ii), we get

Putting the value of b in equation (iii) we get

Thus, the first number is a = 12 and the second number is b = 9.