She underestimated by 60 cents. To get this answer all you need to do is multiply 1 dollar times 12 which is $12 and then multiply $.30 by 12 and that gives you $3.60. Then you add the $12 to the $3.60 and that gives you $15.60 which is 60 cents over the estimation.
You can multiply to cancel out the division
a.
This is the geometric sequence: a1 = 1.5 m = 150
cm, r = 0.74
The formula now is an = a1 x r ^ n-1
Just substitute a1 = 150 cm and r = 0.74
an = 150 x (0.74) ^ n – 1
b.
The second part is:
A6 = 150 x 0.74 ^ 6-1
= 150 x 0.74 ^5
= 150 x 0.221906624
= 33.28509936 cm