Part A
The given expression is
3y - 8x
Given that x = - 4/9 and y = 1/2, by substituting, her answer was
3(1/2) - 8(1/2)
Her mistake was that she put x = 1/2 in the place of x instead of x = - 4/9
The correct expression would be
3(1/2) - 8(- 4/9)
= 3/2 - - 32/9
= 3/2 + 32/9