7√7
using the ' rule of radicals '
• √a × √b ⇔ √ab
simplifying the radicals
√28 = √(4 × 7 ) = √4 × √7 = 2√7
√63 = √(9 × 7) =√9 × √7 = 3√7
√112 = √(16 × 7 ) = √16 × √7 = 4√7
substituting into the expression
3(2√7) - 5(3√7) + 4(4√7) = 6√7 - 15√7 + 16√7 = 7√7
75√109.5=1.46
1.2√79.1=65.92
5.2√9.16=1.76
17.1 =17.1
I was stuck on the same thing in my class test. I ended up failing but if I get the answers to it I’ll totally send them to you!!!
Answer:

Step-by-step explanation:
The area of the big triangle is 1/2 b h = 1/2*6*(12^2 = 6^2 + x^2)
that ends up being 
the small triangle are needs to be subtracted....
that is the length of the unknown side...
1/2 B * h of that triangle get you to 
just subtract the two areas