Question

if DF = 9x-39, find EF.

Answer 1

$DF=DE+EF\\\\DF=9x-39\\DE=47\\EF=3x+10\\\\\text{substitute}\\\\9x-39=47+3x+10\\9x-39=3x+57\ \ \ |-3x\\6x-39=57\ \ \ \ |+39\\6x=96\ \ \ \ |:6\\x=16\\\\\text{put the value of x to the expression}\ 3x+10\\\\EF=3(16)+10=48+10=58$

Answer: EF = 58

Answer 2

The measure of EF is 58

From the line given, DF is equal to the sum of DE and EF

DF = DE + EF

Given the following

DE = 47

EF = 3x+10

DF = 9x-39

Substitute the given values into the formula

47+3x+10 = 9x-39

57+3x = 9x-39

3x-9x = -39-57

-6x = -96

x = -96/-6

x = 16

Get EF

Since EF = 3x+10

EF = 3(16)+10

EF = 48+10

EF = 58

Hence the value of EF is 58

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