J=john
m=mary
j is 2 times as old as mary
j=2 times m
sum is 21
m+j=21
find mary
subsitute
j=2m therefor subsitute 2m for j
m+2m=21
add like terms
3m=21
divide by 3
m=7
mary=7
*HOPE I HELPED!*
"If and only if" (abbreviated "iff") is a biconditional logical connective between two assertions that is either true or untrue. The correct option is D.
<h3>What is "if and only if" operator?</h3>
In logic and related subjects such as mathematics and philosophy, "if and only if" (abbreviated "iff") is a biconditional logical connective between two assertions that is either true or untrue. It is represented by ⇔ or ↔.
The two of the events are
- p: the whole number has one digit.
- q: the whole number is less than 10.
Now, the representation of "the whole number has one digit if and only if the whole number is less than 10" is done as p ↔ q.
Hence, the correct option is D.
Learn more about "if and only if" operator:
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Step-by-step explanation:
Michelle orders soup, or she orders salad goes with disjunction.
The fireworks were loud and colorful goes with conjunction.
If the watch is broken, then it it showing the wrong time goes with conditional.
62-32 = 30
30* 5/9 = 16.666 rounded to 17 degree celius
The answer of that equation is 2 and square root of 2
