Answer:
17
Step-by-step explanation:
AC = AB + BC
Since we know what each variable equals, we can write out the equation as shown:
47 = 5x + 3x - 1
Combining like terms:
47 = 8x - 1
Add 1 on both sides:
48 = 8x
Divide 8 on both sides:
X = 6
Now that we know what X equals, we can solve BC.
BC = 3(6) - 1
BC = 18 - 1
BC = 17
Therefore BC = 17.
Answer:
40/9
Step-by-step explanation:
Use the work formula,
+
=
, where A is the amount of time it takes one person, B is the amount of time it takes another person, and T is the time it takes for them to work together.
Plug in the times for David and Alex alone:
+
= 
Find the least common denominator, which is 40.
+
= 
= 
Cross multiply and solve for T:
9T = 40
T = 40/9
So, if they worked together, it would take them 40/9 hours
A= (a+b+c)h is the formula. I hope this is helpful for you. I am pretty positive it will help.