First bring all terms in 'a' to the left side of the formula by subtracting ac from both sides
ab - ac - cd = ac - ac
ab - ac - cd = 0
now add cd to both sides
ab - ac -cd + cd = cd
ab - ac = cd
now factor the left side by taking out the 'a'
a(b-c) = cd
now divide both sides by (b-c)
a = cd / (b-c)
done
Answer first number = 57 second number = 41
x= 16 + y
x + 2y = 139
16+ y + 2y =139
16 + 3y =139
16-16 +3y = 139-16
3y = 123
3/3y = 123/3
y= 41
x= 16+y
x = 16+41
x= 57
So you follow the steps and i hope this will be easy for you .


By doing cross multiplication.

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Answer:
(78, 80)
Step-by-step explanation:
Given a normal distribution :
Mean = 79 seconds
Standard deviation = 0.5 seconds
Using the empirical rule :
95% of her finishing times :
According to the empirical rule, 95% represents 2 standard deviations from the mean that is ± 2 standard deviations from the mean score or value.
Hence ;
The interval will be defined as ;
Mean ± 2(standard deviation)
79 ± 2(0.5)
79 ± 1
(79 - 1) ; (79 + 1)
78 ; 80