638 Worked-Out Solutions to Exercises: Chapters 11 to 19
Let’s get the equations into SI form. In the first equation, we can subtract x from each
side to get
y=−x+ 44
In the second equation, we can subtract x from each side and then multiply through by
−1 to obtain
y=x− 10
Mixing the right sides of these two SI equations produces this:
−x+ 44 =x− 10
Adding 10 to each side gives us
−x+ 54 =x
Adding x to each side, we get
54 = 2 x
Dividing through by 2, we determine that x= 27. We can plug this into either of the SI
equations to solve for y. Let’s use the second one. We have
y=x− 10
= 27 − 10
= 17
The two numbers are 27 and 17.
- Again, let’s call the numbers x and y. We are told that these two facts are true:
x+y= 100
and
y= 6 x
Actually, we could just as well say that x= 6 y; it doesn’t matter. Let’s stick with the equations
above. The first equation can be put into SI form by subtracting x from each side. That gives us
y=−x+ 100
The second equation is already in SI form (the y-intercept is 0). Mixing the right-hand
sides, we obtain
−x+ 100 = 6 x