If 2x + 3y = 4 and 5x + 6y = 7, what is the value of 8x + 9y ?
A.) 10 B.) 1 C.) 2 D.) 7 E.) 10
Find the values of x and y from the given system of equations, then substitute those values into 8x + 9y.
Solve the system. 2x + 3y = 4 5x + 6y = 7 4x  6y = 8 {multiplied first equation by 2} 5x + 6y = 7 {second equation stays the same}  x = 1 {added the two equations} Substitute the value of x into one of the two equations to solve for y. 2x + 3y = 4 {first equation} 2(1) + 3y = 4 {substituted 1, in for x, into first equation} 2 + 3y = 4 {multiplied 2 by 1} 3y = 6 {added 2 to each side} y = 2 {divided each side by 3} Substitute 1 for x and 2 for y, into the expression 8x + 9y. 8x + 9y = 8(1) + 9(2) {substituted 1 for x and 2 for y} = 8 + 18 {multiplied} = 10 {added} E.) 10 Ask Algebra House Comments are closed.

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