We are to show that if X ⊆ Y then (X ∪ Z) ⊆ (Y ∪ Z) for sets X, Y, Z.
Assume that a is a representative element of X, that is, a ∈ X. By the definition of union, a ∈ X ∪ Z. Now because X ⊆ Y and we assumed a ∈ X, then a ∈ Y by the definition of subset. And because a ∈ Y, then a ∈ Y ∪ Z by definition of union.
We chose our representative element, a, and showed that a ∈ X ∪ Y implies that a ∈ Y ∪ Z and this completes the proof.
Answer:
8 + 2x = 30
Step-by-step explanation:
Given,
The initial number of push-ups he does in each day = 8,
And, the number of push-ups, he increases per day = 2,
Let x be the number of days after he will reach his target of 30 push-ups,
Since, the number of push-ups she will increase in x days = 2x,
Thus, the number of push-ups she will do after x days = 8 + 2x,
⇒ 8 + 2x = 30, which is the required equation.
31.25 is answer , rounded answer would be 30 miles each side.
<span>Let x be the number of songs downloaded.
Each song is $1.29; the total cost would be found by multiplying the cost by the number of songs, or 1.29x.
This cannot be more than 20, so we set this less than or equal to 20:
1.29x ≤ 20.
<u>To solve this, we divide both sides by 1.29: </u>
</span>

<span> ≤ </span>

<span>;
x ≤15.5.
We <u>cannot download half of a song</u>, so we round this down to 15 (although the number rounds up mathematically, he would not have enough money to download 16 songs). This means he can download at most 15 songs.</span>
Answer:
2.45c + 1.65c = 4.12 + 0.75
Step-by-step explanation:
To write an equation to find the value for c, we need to declare what c is first.
c = price of fruit
2.45c + 1.65c = 4.12 + 0.75
Now we multiplied c to 2.45 and 1.65 and added them together, because whatever the value of c is will give us the equivalence of the sum of 4.12 + 0.75.
Now to check if the equation is right, let's solve for c.
2.45c + 1.65c = 4.12 + 0.75
4.1c = 4.87
Now to get the value of c, we divide both sides of the equation by 4.1.

c = 1.19
Now let's substitute the value of c in the equation to see if we got it right.
2.45(1.19) + 1.65(1.19) = 4.12 + 0.75
2.92 + 1.96 = 4.87
4.87 = 4.87
Therefore concluding that the value of c is 1.19.