There are total of 84 students in the robotics club and the science club. the science club has 12 more students than the robotics club. how many students are in the science club?

First off we have x number of students in the robotics club, 12 more in the Science club, and 84 students in total. This means:
Robotics Club = x
Science Club = (x + 12)
Total = 84

Okay, so here's the equation:

x + (x + 12) = 84 ~ Add like terms.
2x + 12 = 84 ~ Subtract 12 by both sides.
2x = 72 ~ Divide both sides by 2.
x = 36 ~ Meaning that the Robotics Club has 36 members.

At this point you can do: 84 - 36 = 48 which gives you the number of members in the Science Club, though...:

36 + (36 + 12) = 84 ~ Add the two in the parenthesis to get your answer.
36 + 48 = 84 ~ 48 is the number of Students in the Science Club.
84 = 84

In conclusion: The Science Club has 48 students.

Hope that helps. ^ ^
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