Solving Systems of Equations: Substitution of Fractions in 2x-y/2 + -3y+x/5 = 7

Question

Solve the following equations for x and y using the substitution method:

{2xy2+3y+x5=7yx85y+x6=4 \begin{cases} \frac{2x-y}{2}+\frac{-3y+x}{5}=7 \\ \frac{-y-x}{8}-\frac{5y+x}{6}=4 \end{cases}

Video Solution

Step-by-Step Solution

To solve the system of equations using substitution:

Step 1: Simplify each equation.

First equation:

2xy2+3y+x5=7\frac{2x - y}{2} + \frac{-3y + x}{5} = 7

Multiply by 10 to eliminate denominators:

(2xy)×5+(3y+x)×2=70(2x - y) \times 5 + (-3y + x) \times 2 = 70 10x5y6y+2x=7010x - 5y - 6y + 2x = 70 12x11y=70(1)12x - 11y = 70\quad\text{(1)}

Second equation:

yx85y+x6=4\frac{-y - x}{8} - \frac{5y + x}{6} = 4

Multiply by 24 to eliminate denominators:

(yx)×3(5y+x)×4=96( -y - x) \times 3 - (5y + x) \times 4 = 96 3y3x20y4x=96-3y - 3x - 20y - 4x = 96 7x23y=96(2)-7x - 23y = 96\quad\text{(2)}

Step 2: Solve the first equation for xx:

12x=70+11y12x = 70 + 11y x=70+11y12(3)x = \frac{70 + 11y}{12}\quad\text{(3)}

Step 3: Substitute Equation (3) into Equation (2):

7(70+11y12)23y=96-7\left(\frac{70 + 11y}{12}\right) - 23y = 96

Clear while multiplying by 12:

7(70+11y)276y=1152-7(70 + 11y) - 276y = 1152 49077y276y=1152-490 - 77y - 276y = 1152 353y=1642-353y = 1642 y=4.65y = -4.65

Step 4: Substitute y=4.65y = -4.65 back into Equation (3) to find xx:

x=70+11(4.65)12x = \frac{70 + 11(-4.65)}{12} x=7051.1512x = \frac{70 - 51.15}{12} x=18.8512x = \frac{18.85}{12} x=1.57x = 1.57

Therefore, the solution to the problem is x=1.57 x = 1.57 , y=4.65 y = -4.65 .

Answer

x=1.57,y=4.65 x=1.57,y=-4.65