To solve for this, we need to write out each multiple of 3 that's a double-digit (##) before we hit a triple-digit (###). Once we do that, count the even numbers.
Let's start:
12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48, 51, 54, 57, 60, 63, 66, 69, 72, 75, 78, 81, 84, 87, 90, 93, 96, 99,
First, let's count how many multiples of 3 we have.
We have 30 double-digit multiples of 3.
Now, let's count how many double-digit numbers are even.
I will recount starting from the first even double-digit number.
10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98.
Let's count how many even double-digit numbers we have.
We have 45 even double-digit numbers.
Your answers are:
30 double-digit multiples of 3.
45 even-double-digit numbers.
Hope this helps!