Answer:
418 4/10
Step-by-step explanation:
To answer this we subtract 450 7/10 from 869 1/10.
We must borrow a '1' from 869 1/10: 868 11/10
Now subtract 450 7/10 from 868 11/10:
418 4/10 (CHANGE IN ELEVATION)
This reduces to 418 2/5.
If the average rates were 20 and 25 miles per hour, then together they cover 45 miles of the distance they are separated by per hour. The ships will be 30 miles apart when 270 miles have been covered, so it takes 270/45=6 hours to cover the distance. 6 hours after 5 PM is 11:00 PM.
Combining the operations
The allowed operations are:
Add the same amount to both sides (either x's or ones)
Subtract the same amount from both sides (either x's or ones)
Multiply both sides by the same number (but not by zero)
Divide both sides by the same number (but not by zero)
(There are others, too, but they are not needed in simple equations.)
The goal is to FIRST add and subtract until we have ONLY x's (blocks) on one side and ONLY ones (circles) on the other. Then, if you have more than one block, you need to divide so as to arrive to the situation with only one block on the one side, which is the solved equation!
