unfortunately they're both incorrect.
the pythagoras formula says that in a right triangle:
(hypotenuse of the triangle)²= (cathetus 1) + (cathetus 2)
[easier said, if one if the angles in the triangle is 90° then, (long side)²= (short1)² + (short2)²]
in the exercises that you made, you did:
(short1)²=(long side)²+(short side2)², and this formula isn't correct.
Tip: if you're not sure which one the long side is, bc ots not clear on the drawing, it is always the one facing the right angle
answers:
6.
8²= x² + 3.7²
x²= 8²-3.7²
x²= 64- 13.69
x²= 50.31
x= V50.31
x≈ 7.1
7a.
9.8²= x+ 4²
x²= 9.8²-4²
x²= 96.04 - 16
x²= 80.04
x= V80.04
x≈8.9
7b.
cos A= |AC| / |AB|
Cos A= 4.0 / 9.8
A= 65°54'38"
A= 66°
8.
sin A= |BC| / |AC|
sin A= 8/12
A= 41°48'37"
A= 41°
hope this helps :)