Answer:
The number of baseball card to begin with is 143
Step-by-step explanation:
Let The number of baseball cards = x
The number of sold baseball card = 60% of x
= 0.6 x
The number of left baseball card = x - 0.6 x = 0.4 x
The number of card gave away = 30 % of left cards
= 0.3 × 0.4 x = 0.12 x
The number of card left in his possession = 40
So, 0.6 x + 0.12 x + 40 = x
Or, 40 = x - 0.6 x - 0.12 x
Or, 40 = 0.28 x
∴ x = 
= 142.85 ≈ 143
Hence The number of baseball card to begin with is 143 Answer
You did not include the choices. However, I answered one that just included them. I've included the possible answers below and then the correct answers.
<span>A multiple of Equation 1.
B. The sum of Equation 1 and Equation 2
C. An equation that replaces only the coefficient of x with the sum of the coefficients of x in Equation 1 and Equation 2.
D. An equation that replaces only the coefficient of y with the sum of the coefficients of y in Equation 1 and Equation 2.
E. The sum of a multiple of Equation 1 and Equation 2.
</span>A, B and E.
Adding and multiplying the terms allow them to keep working. However, you must make sure that each variable is changed each time. Not just one as in C and D.
They are both going 14 meters per second so therefor they will be the same distance apart the whole time.
Let's take an example to illustrate this case:
<span>positive fraction = 2/7
</span>
<span>negative fraction = - 3/5
Now we need to subtract </span><span>- 3/5 from 2/7
Right?
2/7 - (-3/5) = 2/7 + 3/5
here we need to unify the denominators as follows:
the lowest common factor between 7 and 5 is 35
2/7 = 10/35
3/5 = 21/35
Now back to </span><span>2/7 + 3/5:
</span><span><span>2/7 + 3/5 = 10/35 + 21/35 = (10+21)/35 = 31/35
That's it
Hope that helps you</span>
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