Let's put more details in the given figure to better understand the problem:
Since it appears that the two triangles formed are similar triangle, we can determine the height of the building by ratios and proportions,
We get,
[tex]\text{ }\frac{\text{ h}}{\text{ 170}}\text{ = }\frac{\text{ 6}}{\text{ 3.5}}[/tex][tex]\text{ h x 3.5 = 6 x 170}[/tex][tex]\text{ 3.5h = 1,020}[/tex][tex]\text{ }\frac{\text{3.5h}}{\text{ 3.5}}\text{ = }\frac{\text{1,020}}{\text{ 3.5}}[/tex][tex]\text{ h = }291.42857142857\text{ }\approx\text{ 291 Feet}[/tex]
Therefore, the height of the building is approximat291 Feet.