Answer:
You have 500 marbles.
The longest side of the biggest equalateral triangle that you can make with your marbles is 31
Step-by-step explanation:
28 + 4 = 32
So our equation is:
TR(32) - 28
Now find Triangular Number 32: (32 *33)/2=528
528 - 28 = 500
So, we have 500 marbles
Now we need to find the longest side of the biggest equalateral triangle that you can make make with your marbles
Let's go back to 28 + 4 = 32
One row above 32 is 31
So the longest side of the biggest equalateral triangle that you can make with your marbles is 31
Hope this helps!