Answer:
let the grade points be a,b,c
a+b+c=258
b=c+10( since she noticed that on tests two and three,she scored 10 points fewer).
<QOS =150°(opp. <'s of a cyclic quard)
<QRS=75°(< at centre =2×< at circumference)
I don't know about the third one bro
Maybe there's an erroron that quation
I think the picture here explains you everything
hope this helped
