Answer:
a = -2
Step-by-step explanation:
7a + 10 = 2a
subtract 7a from each side
7a-7a+10 = 2a-7a
10 = -5a
divide by -5
10/-5 = -5a/-5
-2 = a
check
7 (-2) +10 = 2(-2)
-14 + 10 = -4
-4 = -4
<u>Answer:</u>
A = 70
B = 90
<u>Step-by-step explanation:</u>
We know that Car A travels 20 mph faster than Car B.
Assuming the speed of Car B to be x and the speed of Car A to be x+20, we can write:

Taking the reciprocal of both sides to make x the subject:




---> speed of Car A
Finding the speed of Car B: 
Therefore, the speed of Car A = 70 and the speed of Car B = 90.
To solve problems like this you can either graph or solve mathematically. To do the ladder we need to solve for one variable at a time. So lets cancel one variable out.
Multiply equation 1 by 2
This will give 4x-2y=14
Now we can get rid of y by subtracting 2 from 1
This will give x=9
Plug back in to either equation, i will use equation 2
3(9)-2y=5 simplify
-2y=-22 solve
Y=11