−3y − 9y + 5y = 2,1
−7y = 2,1
y = 2,1 : (−7)
y = −0,3

−2,4m + 3,8m + 1,2m = −0,052
2,6m = −0,052
m = −0,052 : 2,6
m = −0,02

$-\frac{3}{7}a + \frac{5}{6}a - \frac{8}{21}a = -\frac{1}{49}$
$-\frac{18}{42}a + \frac{35}{42}a - \frac{16}{42}a = -\frac{1}{49}$
$\frac{1}{42}a = -\frac{1}{49}$
$a = -\frac{1}{49} : \frac{1}{42}$
$a = -\frac{1}{49} * \frac{42}{1}$
$a = -\frac{1}{7} * \frac{6}{1}$
$a = -\frac{6}{7}$

$-8\frac{7}{16}c + 10\frac{19}{24}c - 3\frac{3}{8}c = -3\frac{1}{16}$
$-8\frac{21}{48}c + 10\frac{38}{48}c - 3\frac{18}{48}c = -\frac{49}{16}$
$-1\frac{1}{48}c = -\frac{49}{16}$
$-1\frac{1}{48}c = -\frac{49}{16} : (-\frac{49}{48})$
$c = -\frac{49}{16} * (-\frac{48}{49})$
$c = -\frac{1}{1} * (-\frac{3}{1})$
с = 3

2,3x − (−7,2) * x + x * (−1,5) = −2,4
2,3x + 7,2x − 1,5x = −2,4
8x = −2,4
x = −2,4 : 8
x = −0,3

3,4y + y * (−8,1) − (−2,2) * y = −10
3,4y − 8,1y + 2,2y = −10
−2,5y = −10
y = −10 : −2,5
y = 4