A step by step answer please

7.92 m.

Step-by-step explanation:

Mean height = ∑(f . x) / ∑f  where  x is the midpoint and f the frequencies

The midpoints for the heights are:

2 for frequency 8              ( 0 + 4)/ 2 = 2

6 for      ..           21

10 for    ..            12

14 for    ..              7

18 for   ..               2

So the mean is:

[(2*8) + (6*21) + (10*12) + (14*7) + (18*2) ] / (8 + 21+12+7+2)

= 396 / 50

= 7.92 m.

$450 is the answer.

step-by-step explanation:

30% of 450 = 135

450-135=315

you can first factor out the n to get n(1+5). we know that 1+5 is 6, so we just have 6n.