Fred is 4 times as old as Nathan and is also 27 years older than Nathan.

The strategy is to work from a system with three variables and three equations down to something with two variables and two equations. In a two variable-two equation system, you can use either substitution or elimination.

First, let's organize the equations.

(1) x + y = 8

(2) y + z = 7

(3) x + z = 5

Now, we'll solve one of (1), (2), and (3) for a variable. The choice is yours, but we'll use equation (3) and solve it for x.

x + z = 5

x = 5 - z.

Now we put this into equation (1). Why (1)? It's the only one of (1) and (2) with x.

x + y = 8

5 - z + y = 8

-z + y = 3

y - z - 3 to rearrange it.

Now look at this new equation - call it (4) and the original (2).

(4) y - z = 3

(2) y + z = 7

This is a system of two equations and two variables. Either substitution or elimination works here - let's use elimination because of the -z and +z.

y - z = 3

y + z = 7

We add them together and we have that 2y = 10. Divide on both sides and y = 5. One variable down, two to go.

Now we go back to original equation (2). Substitute y = 5 to find z.

y + z = 7

5 + z = 7

z = 2.

Two down, one to go. Since we know z = 2, let's put it into (3) and find x. (Equation (1) with y = 5 works fine as well.)

x + z = 5

x + 2 = 5

x = 3

Thus x = 3, y = 5 and z = 2.

3 0

3 years ago

Someone Explain to me how 5. Is valid ???

vichka [17]

This is valid through the law of syllogism. If you swap lines 1 and 2, then you'll have this argument:

If I step on a beehive, then I will get stung.

If I get stung by a bee, then it will hurt.

Therefore, if I step on a beehive, then it will hurt

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So it's like connecting a chain together. Point A (stepping on the hive), leads to point B (getting stung), which leads to point C (getting hurt). We can take a shortcut to bypass point B to jump from A to C in one step. Check out the attached image for a visual of what I'm referring to.

6 0

3 years ago