add the two equations together
5a+5b=25
-5a+5b=35
------------------
0 + 10b =60
divide by 10
b=6
5a + 5b = 25
5a +5(6) = 25
5a +30 =25
subtract 30 from each side
5a =-5
divide by 5
a = -1
Answer (-1,6)
or a=-1 b=6
Answer:
4.
°
Step-by-step explanation:
Given:
The tangent of the angle is given as:

Since the angle is negative, it means that it is measured in the clockwise direction as angles measured in clockwise direction are negative and that measured in counter clockwise directions are positive.
-212° when measured from counter clockwise direction will be equal to:

Therefore,
= 
Now, we have the identity for tan as:

Here, 
Therefore,

Hence,
=
=
°
Answer:
Eric's expression is :

and Andrea's is :

In Eric's expression, 20 represents the initial amount of substance with which he has started the experiment.
is the amount of substance left after each time period (in this case, each week).The variable w in this case represents the number of weeks.
Andrea's expression can be written as :

The one outside of parentheses represents the initial amount of the substance. The one inside of parentheses represents 100% of the original amount of the substance. 0.5 represents the 50% of the substance that is lost each time period. The variable w in this case represents the number of weeks.
Answer:
7, 17, 20, 11
Step-by-step explanation:
you just round each number to the nearest whole number and then add them