We know that:
r = -18
s = 27
t = -15
You want to find the value of r - s - t
Frist plug each corresponding value into r - s - t
-18 - 27 - (-15)
To solve this you will need to subtract from left to right.
-18 - 27 - (-15)
-18 - 27 <<< When subtracting with a negative number you will do something called "Same-Add-Opposite." This means that you will keep the first number in the expression (in this case that is -18) the same. Then turn the subtraction sign into an addition sign. Finally you will take the "opposite" sign of the second number. When I say "opposite sign" I mean that if this number is positive it will become negative. If it was negative it will become positive.
Here is your expression after applying same - add - opposite:
-18 + (-27)
When adding a negative number with a negative number you will simply just add the two numbers together and the sign of the answer will be negative as well.
-45
This is the remaining expression:
-45 - (-15)
^^^Apply same - add - opposite to this as well
-45 + 15
When adding a positive number with a negative number you will act as if you are subtracting the two numbers, then take the sign of the largest number (disregarding the signs). In this case the largest number is 45 (disregarding the signs) and its sign is negative. Your answer will have a negative sign.
-30
Hope this helped!
~Just a girl in love with Shawn Mendes
