5x + 60y = 35
x +y = 1.5 : rewrite as x = 1.5-y and substitute this formula for x in the first one:
5(1.5-y) + 60y = 35
distribute:
7.5 - 5y + 60y = 35
combine like terms:
7.5 + 55y = 35
subtract 7.5 from both sides:
55y = 27.5
divide both sides by 55 to solve for y
y = 27.5 / 55 = 0.5
now substiute 0.5 for y in the 2nd equation:
x + 0.5 = 1.5
x = 1.5 - 0.5 = 1
he walked for 1 hour
