Justin's sand castle is 180 cm tall but the wind is blowing away sand at a rate of 8 cm per minute. Taylor's sand castle is 160 cm tall and she is adding sand to it at a rate of 6 cm per minute. After how many minutes will their sand castles be at an equal height?

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb

12*c

step-by-step explanation:

do you have a picture of the table