Question 851366
(4*84+96*X)/(4+X)=90
(336+96X)/(4+X)=90
90(4+X)=336+96X
360+90X=336+96X
90X-96X=336-360
-6X=-24
X=-24/-6
X=4 TESTS OF A GRADE OF 96 IS NEEDED.
PROOF:
(4*84+96*4)/(4+4)=90
(336+384)/8=90
720/8=90
90=90