Answer: 29 ft
Step-by-step explanation:
You can calculate the height at which the ladder touches the wall by applying the pythagorean theorem, which is:
[tex]a^{2}=b^{2}+c^{2}[/tex]
Where a is the hypotenuse and b and c are the legs.
You have that:
[tex]a=30ft\\b=7.5ft[/tex]
Then solve for the other leg:
[tex]c=\sqrt{a^{2}-b^{2}}=\sqrt{(30ft)^{2}-(7.5ft)^{2}}=29ft[/tex]
