Question

4. If DF = 9x - 39, find EF. Help I’m so confused!!!!

Answer 1

Answer:

EF =58

Step-by-step explanation:

from the illustration,

EF =DF - DE

given that DF =9x-39 , DE =47 EF=3x +10

substitute them into the formula,

3x +10=9x-39 - 47

solving for x

3x +10 =9x -86

grouping like terms

3x - 9x =-86 -10

-6x=-96

dividing through by -6

$\frac{ - 6x}{ - 6} = \frac{ - 96}{ - 6}$

$x = \frac{96}{6}$

$x = 16$

but EF=3x+10

substitute x=16 into it to get the EF

EF= 3(16)+10

EF=48+10

EF=58

Answer 2

$\huge\boxed{58}$

First of all, we know that $DE+EF=DF$, because these are two segments that make up one larger segment.

Write this as an equation.

$DE+EF=DF$

$47+(3x+10)=9x-39$

Remove the parentheses. $47+3x+10=9x-39$

Combine the like terms. $3x+57=9x-39$

Subtract $9x$ from both sides. $-6x+57=-39$

Subtract $57$ from both sides. $-6x=-96$

Divide both sides by $-6$. $x=16$

Now, find $EF$.

$3x+10$

$3(16)+10$

Multiply. $48+10$

Add. $\boxed{58}$