Answer:
Systematic sampling
Step-by-step explanation:
An EPA contractor needing to test the concentration of a substance in ten samples out seventy samples provided form a single source at regular time intervals.
For the contractor to effectively carry out the testing he has to employ a Non-probability system of sampling which is called Systematic sampling, because in systematic sampling we can assume the population size (x ) which in this case is 70 and the sample size( n ) to be 10
He will have to select ; ( x / n )^th of the sampling frame for best results
12 • 4 = 48
25% of his mom's age is benny's age
<u>Answer-</u>
<em>The correct answer is</em>
<em>∠BDC and ∠AED are right angles</em>
<u>Solution-</u>
In the ΔCEA and ΔCDB,

As this common to both of the triangle.
If ∠BDC and ∠AED are right angles, then 
Now as
∠BCD = ∠ACE and ∠BDC = ∠AED,
∠DBC and ∠EAC will be same. (as sum of 3 angles in a triangle is 180°)
Then, ΔCEA ≈ ΔCDB
Therefore, additional information can be used to prove ΔCEA ≈ ΔCDB is ∠BDC and ∠AED are right angles.
It bisects so DE=EF
DE=5y
EF=13y-8
so
5y=13y-8
minus 13y both sides
-8y=-8
divide both sides by -8
y=1
DE=5y=5(1)=5
DE=EF=5
DF=DE+EF=5+5=10
DE=5
EF=5
DF=10