Greetings from Brasil...
We will pass the - 2 to the 1st member
2 + [1/(X + 7)] = 15/(5(X + 7))
simplifying the numerator and denominator of the 2nd member
2 + [1/(X + 7)] = 3/(X + 7)
solving the sum of the 1st member
(2X + 15)/(X + 7) = 3/(X + 7)
product of the means by extremes
(2X + 15) · (X + 7) = 3 · (X + 7)
2X² + 15X + 14X + 105 = 3X + 21
2X² + 29X - 3X + 105 - 21 = 0
2X² + 26X + 84 = 0
solving this 2nd degree equation
Δ = b² - 4.a.c
Δ = 26² - 4 . 2 . 84
Δ = 676 - 4. 2 . 84
Δ = 4
X' = (-26 + √4)/2.2 X'' = (-26 - √4)/2.2
X' = -24 / 4 X'' = -28 / 4
X' = -6 X'' = -7
