bonsoir
a = 0 x + x = x
b = xy + xy = 2 xy
c = xy * yx = x²y²
d = 10 x
e = 2 x * 7 x² = 14 x ³ ( * = multiplier)
f = xy - y
g = - 3 x + 2 ( 5 x + 1 ) = - 3 x + 10 x + 2 = 7 x + 2
h = 7 xy + 8 * 6 x² = 7 xy + 48 x²
i = 8 y + 15 - 2 y = 6 y + 15
j = 3 x² - x + 7 x - x² = 2 x² + 6 x