Answer:The value of a - b + c + d = -4Step-by-step explanation:* Lets explain the linear equation- The linear equation is the equation that represented graphically by a line - The general form of its equation is ax + by = c- The slope of the line is -a/b and the y-intercept of the line is c/a, where a is the coefficient of x , b is the coefficient of y and c is the numerical term∵ We have two linear equation in the problem∴ Their general form is ax + by = e , cx + dy = f∵ The equation are 2x + 8y = 7 and 4x - 2y = 9- By comparing the two equations with their general forms∴ a = 2 , b = 8 , c = 4 , d = -2- Now we can find the value of a - b + c + d∵ a = 2 , b = 8 , c = 4 , d = -2∴ a - b + c + d = 2 - 8 + 4 + (-2) = 2 - 8 + 4 - 2 = -4 * The value of a - b + c + d = -4