Question 144961
Speed of jet = j
Speed of wind = w

1800/(j+w) = 3 (took 3 hours with a tailwind)
1800/(j-w) = 4 (took 4 hours with a headwind)
1800 = 3(j+w)
1800 = 4(j-w)
3j + 3w = 1800
4j - 4w = 1800
j + w = 600
j - w = 450
Add the 2 eqns
2j = 1050
j = 525
w = 75