So let's take a peek at both's ages, keep in mind, every year, is 1year added to Irene and 1year added to Fred
so... if we look at their ages
notice, Fred is always 40years older than Irene
thus, whatever age Irene is, let's say "i", then Fred is " i + 40 "
now, when is Fred 5 times Irene's age or 5*i or 5i? well,
f = fred's age i = irene's age
f = i + 40
now if f = 5i
5i = i + 40 <--- solve for "i" to see how old Irene was then
5 - n written in word form is:
Five minus a number, n.
The key is to find the first term a(1) and the difference d.
in an arithmetic sequence, the nth term is the first term +(n-1)d
the firs three terms: a(1), a(1)+d, a(1)+2d
the next three terms: a(1)+3d, a(1)+4d, a(1)+5d,
a(1) + a(1)+d +a(1)+2d=108
a(1)+3d + a(1)+4d + a(1)+5d=183
subtract the first equation from the second equation: 9d=75, d=75/9=25/3
Plug d=25/3 in the first equation to find a(1): a(1)=83/3
the 11th term is: a(1)+(25/3)(11-1)=83/3 +250/3=111
Please double check my calculation. <span />
Answer/Step-by-step Explanation:
Given:
a = no. of DVDs
b = no. of CDs
Total cost ($) for DVDs and CDs = 
a. The cost for 1 DVD = 2.5(a) = 2.5(1) = $2.5
The cost for 1 CD = 2(b) = 2(1) = $2
b. Total cost for 4 DVDs and 4 CDs:
Substitute a = 4, and b = 4 into the equation.
Total cost for 4 DVDs and 4 CDs = $18
c. To find out if $20 would be enough to buy 6 DVDs and 3 CDs, substitute a = 6, and b = 3 into the equation. Solve for the total cost to see if it equals $20 or is less than $20. If it's greater than $20, then it won't be enough.
6 DVDs and 3 CDs cost more than $20, therefore, $20 is not enough.
