Respuesta :

(H=highest, & L=lowest )

H= 42 + L = 138

42 + L + L = 138 

2L = 138 - 42 

2L = 96 

L = 48 

So the lowest grade would have to be "48"

x+42=138
x=138-42
x=96
when you put the numbers the sum should be equal 
x(96)+42=138
96+42=138
138=138
hope it helps!!
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