Nine Times A Number, Decreased By 15, Is Equal To The Sum To The Sum Of 3 And Six Times The Number. Find The Number?

Let the number is x, then according to the given conditions;

9x - 15 = 3 + 6x

9x - 15 - 3 - 6x =0

(9-6)x - (15 + 3) = 0

3x - 18 = 0

3x = 18

x = 6

So, the required number is 6.