Peter and Diane have the same average in mathematics. on the next test, diane scored 97%, and her average improved to 90%, put peter scored 73% and his average decreased to 87%. how many tests had preceded the last test?

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endurance - First define your variables: m = the mean or average n= how many tests had preceded the last test Now, write down your equations: Diane: (m*n + 97)/(n+1) = 90 Peter: (m*n + 73)/(n+1) = 87 Now, simplify by multiplying both equations by (n+1) Diane: (m*n + 97) = 90n + 90 Peter: (m*n + 73) = 87n + 87 Now subtract one equation from the other and the m*n term will cancel out Finally, simply solve for n=7 Hope that helps!