Word problem is a topic that involves interpreting a given statement into a mathematical expression. Thus the answers to the question are:
1. r + 2 = 2r
r = 2
2. d = st
3. b = 4r
There are 9 red cards in the pile.
Word problem is a topic that involves interpreting a given statement into a mathematical expression. This often requires representing the unknown in the statement by an alphabet. So that the value that the alphabet represents is to be determined.
Word problems can be easily interpreted a sentence at a time. And it usually gives an algebraic expression.
In the given question, we have:
a) The sum of a number and two is twice the number.
Let the number be represented by r, we have;
r + 2 = 2r
So that by collecting like terms,
2r - r = 2
r = 2
b) Lorrae swims laps at a constant speed, s, for 2 hours.
The speed, s, of an object is the rate of the distance moved, d, to the time taken, t.
i.e speed, s, = [tex]\frac{distance}{time taken}[/tex]
So that,
distance = speed * time taken
This implies that,
d = s * t
d = st
c) The number of black cards in a pile is 4 times the number of red cards. There are 36 black cards in the pile.
Let the number of black cards be represented by b, and that of red cards be r.
So that;
b = 4r
Given that b = 36, then;
r = [tex]\frac{36}{4}[/tex]
= 9
There are 9 red cards in the pile.
For more clarifications on word problems, visit: https://brainly.com/question/10731035
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