Are you familiar with decimals? It's just an extension of the basic place value you've learned about before. Think of the number 21. "2" is in the tens place, and "1" is in the ones place.
Well, in this question, "1" is still in the ones place. HOWEVER, we have another number AFTER something called a decimal point (.), which shows that now we're getting into digits less than one. "5" is in what's called the tenths place, in which all the numbers are less than one. In other words, 1.5 is equal to 1 + 0.5. 0.5 is less than one, because it is a number in the tenths place.
Obviously, 1+1=2, right? And 2 is less than 3. Well, since 0.5 is even LESS than 1, 1+0.5 is less than 2. Therefore, 1.5 is less than 2, which is less than 3. So, 1.5 is LESS than 3, not greater than.
Answer: No, it's the other way around! 1.5 is LESS than 3.