Introduction:
In this question, we will be converting the fraction 28/-70 into standard form.

Steps to Convert Fraction into Standard Form:
To convert a fraction into standard form, we need to follow a few simple steps:

1. Find the greatest common factor (GCF) of the numerator and denominator.
2. Divide both the numerator and denominator by the GCF.
3. Write the fraction in the standard form, which is a fraction with a positive numerator and a positive denominator.

Now, let's apply these steps to convert 28/-70 into standard form.

Step 1: Find the GCF of 28 and -70
The GCF of 28 and -70 is 14.

Step 2: Divide both the numerator and denominator by 14
28/14 = 2 and -70/14 = -5.

Step 3: Write the fraction in standard form
Since the numerator and denominator have opposite signs, we need to make them both positive. We can do this by multiplying both the numerator and denominator by -1.

2/-5 is the standard form of 28/-70.

Conclusion:
In conclusion, the standard form of 28/-70 is 2/-5. We followed the steps of finding the GCF, dividing both the numerator and denominator by the GCF, and writing the fraction in standard form.