Answer:
D and C
Step-by-step explanation:
<h2>
Answer:</h2>
17
<h2>
Step-by-step explanation:</h2>
Cost per Packet * Number of Packets + Shipping = Amount to Spend
0.90 * b + 2.50 = A
You can spend a maximum of $18.50
A < 18.50
Rearrange the formula to find b
Number of Packets = Amount to Spend - Shipping / Cost per Packet
18.50 - 2.50 = 16.00 / 0.9 = 17.7...
You can't have 0.7 of a packet so you have to round down to 17.
Now if you put it into the original formula:
0.90 * 17 + 2.50 = 17.80
And 17.80 is less than 18.50.
-k-(-8k)
= -k + 8k (two negatives equal one positive)
= 8k-k (flip it around because of the commutative property)
=7k (basic subtraction)
I really hope that helped :)
Try this solution:
let the unknown two-digits number be 'xy'.
Then it is possible to write any two-digit number as 10x+y, where x - the tens digit and y - the unit digit.
Using the rule described above the phrase 'the tens digit of a number is twice the units digit' may be written as x=2y.
Using the same rule the phrase 'if the digits are reversed, the new number is 36 is less than the original number' may be written as (10x+y)-(10y+x)=36.
These two equations may be resolved as system of two equations:

Check: the original number is 84, the new number is 48; difference is 84-48=36.
answer: 84