Probably not too hard. You just need to know the proper physics formulae to plug the numbers into.
Max probably knows all the formulae off the top of his head and could answer this easily.
It's been a very long time since I've thought about any of these formulae, but I might be able to wing it and do the equations without the formulae.
Assume the acceleration due to gravity on Earth is 9.81ms* and that the radius of the moon is 1737.1km and its mass is 1/80 that of Earth.
Did they give an assumed radius of the Earth?
I can assume 6371 kilometers, but if they are assuming a slightly different number, their end result will be slightly different.
I'm also assuming that 23.873 kg is referring to that weight under Lunar gravity (otherwise there would be no point in calculating the Lunar gravity). If the equations are supposed to be based on 23.873 kg under Earth gravity, that's going to lead to a completely different result.
"acceleration due to gravity on Earth is 9.81 m/s²"
"its mass is 1/80 that of Earth"
divided by 80
is 0.122625 m/s²
That's how much the Moon's gravity decreases due to its lower mass.
"the radius of the moon is 1737.1 km"
"radius of the Earth? I can assume 6371 kilometers"
squared is 40,589,641
squared is 3,017,516.41
divided by 3,017,516.41
That's how much the Moon's gravity increases due to its smaller radius.
multiplied by 13.451340600994444964758286103239
is 1.6494706411969438138034848334097 m/s²
So that's the calculation for gravity on the Moon. Now onto the tie.
"2.2mm thick and has a width of 42mm"
multiplied by 42 mm
gives the tie a cross section of 92.4 mm²
divided by 1,000,000
gives the tie a cross section of 0.0000924 m²
"assuming the breaking strain of the material is 23.873 kg/m²"
multiplied by 0.0000924 m²
is 0.0022058652 kg
a mass of 0.0022058652 kg
multiplied by a Lunar gravity of 1.6494706411969438138034848334097 m/s²
results in a force of 0.00363850988583802470522438683275 newtons
Let me know if they have a different assumed radius for the Earth.