10 students averaged 80, so the sum of their scores was (10 x 80) = 800
20 students averaged 89, so the sum of their scores was (20 x 89) = 1,780
All together, the sum of all 30 scores was (800 + 1,780) = 2,580
30 students totaled 2,580, so their average was (2,580 / 30) = <em> 86</em> .
The answer t our question is the first one
I just substituted he number one in every x
The original equation is equal to 147 when x equals to 1
And the first option is also equal to 147 when x equals to one
