Answer:
3x+4=3*2+4
3*2+4=6+4
6+4=10
10=10
19^2 + x^2 = 21^2
19^2 = 361
21^2= 441
361 + x^2 = 441
x^2 = 441-361 = 80
x = sqrt(80) = 8.944 round to nearest tenth = 8.9
