Respuesta :

ashish4112119

Step-by-step explanation:

54^2 + a^2 = 90^2

2916 + a^2 = 8100

a^2 = 8100 - 2916

a^2 = 5184

take the square root of 5184

a = 72

you could have also guessed that its a 3 4 5 right triangle

all the sides are multiples of 3 4 or 5