To express the fraction 9/10 as a decimal, you simply divide the numerator (9) by the denominator (10). Performing this division gives you:
9 ÷ 10 = 0.9
Thus, 9/10 as a decimal is 0.9. This means that if you have 9 parts out of a total of 10, it can be represented as 0.9 in decimal form.