Question 168697
We'll go to the Least score which is "90" to get "A" Grade
{{{Average=90=A}}} -----> {{{system(G1=85,G2=88,G3=90,G4=98,G5=G5)}}}
{{{(G[1]+G[2]+G[3]+G[4]+G[5])/5=90}}}, EQN 1
{{{(85+88+90+98+G[5])/5=90}}}, cross multiply
{{{361+G[5]=90*5=450}}}
{{{G[5]=450-361}}}
{{{highlight(G[5]=89)}}} -----> Final score to have "A" Grade 
Check it out in EQN 1:
{{{(85+88+90+98+highlight(89))/5=90}}}
{{{450/5=90}}}
{{{90=90}}}
Thank you,
Jojo