Question

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Answer 1

a certain amount of money at 2% interest a

first step: give a name to "certain amount of money". people often use x

Answer 2

$800 more than that amount in another account at 4% interest.

any idea how to change that into math?

800 more than x
800+x at 4% interest

Answer 3

do you know the formula to find interest ?

Answer 4

can you find it ? use
http://math.about.com/od/businessmath/ss/Interest.htm

Answer 5

Yes, if you have choices, you can check each one.
If you did not have choices (more like the real world) you would think like this:
x * 0.02 + (x+800)*0.04 = 92

written using the usual algebra "standards" (i.e. we leave out the multiply sign, and put numbers in front of letters):

0.02x + 0.04(x+800)= 92

to find x, distribute the 0.04 (which means multiply 0.04 times each term inside the parens):
0.02x + 0.04x + 0.04*800 = 92

combine 0.02x + 0.04x to get 0.06x
simplify 0.04*800 = 32
0.06x +32 = 92

add -32 to both sides
0.06x +32 - 32 = 92 - 32
0.06x = 60
divide both sides by 0.06
x = 60/.06

if you don't have a calculator, you can multiply top and bottom by 100 to get
x= 6000/6
x= 1000
and
x+800 (the larger amount) is 1800