A staircase has 105 blocks, how many stairs does it have?

1 1
2 3
3 6
4 10
5 15
6 21
7 28
8 36
9 45
10 55
11 66
12 78
13 91
14 105
15 120
16 136
17 153
18 171
19 190
20 210
21 231
22 253
23 276
24 300

Here’s a chart to aid in understanding the staircase issue. Observe that for 1 step, there is 1 block; for 2 steps, 3 blocks; for 3 steps, 6 blocks, and so forth. Note that the blocks corresponding to each step are a combination of that step and all the blocks used in the steps beneath it. For instance, constructing 14 steps requires 105 blocks.
If you’re familiar with summation, you would sum the blocks for each step with all the steps below it. For example, 5 steps would require 5 + 4 + 3 + 2 + 1, resulting in a total of 15 blocks. I hope this helps you begin. As for the second part, I'm confused by the problems since they don't represent equations. NO equal signs


glad if it helps