To write the expression "BX5" as a decimal, we need to determine the numerical value of each letter. In this case, the letters B and X represent unknown values, so we can consider them as variables.
Let's say B = 2 and X = 3:
BX5 = 235
Thus, if B = 2 and X = 3, the decimal form of the expression "BX5" would be 235.