Although it has not been clearly mentioned, it appears that questioner has given the lengths of sides of #color(red)"six"# triangles.

Let these be

#DeltaA-(3, 5, 7)#

#DeltaB-(4.5, 6, 7.5)#

#DeltaC-(6, 8, 9)#

#DeltaD-(1.2, 2.5, 3.1)#

#DeltaE-(8, 15, 17)#

#DeltaF-(14, 19, 21)#

In a **right angled triangle** say #Delta-(P,Q,R)#, if #R# is the largest side, then #R^2=P^2+Q^2#.

In an **acute angled triangle** say #Delta-(P,Q,R)#, if #R# is the largest side, then #R^2 < P^2+Q^2#.

In an **obtuse angled triangle** say #Delta-(P,Q,R)#, if #R# is the largest side, then #R^2 > P^2+Q^2#.

Hence as #7^2 > 3^2+5^2#, #DeltaA# is obtuse angled triangle.

As #7.5^2 = 4.5^2+6^2#, #DeltaB# is right angled triangle.

As #9^2 < 6^2+8^2#, #DeltaC# is acute angled triangle.

As #3.1^2 > 1.2^2+2.5^2#, #DeltaD# is obtuse angled triangle.

As #17^2 = 8^2+15^2#, #DeltaE# is right angled triangle.

As #21^2 > 9^2+14^2#, #DeltaF# is obtuse angled triangle.