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Answer:
Weight=686.7N,
, S.G.=0.933, F=17.5N
Explanation:
So, the first value the problem is asking us for is the weight of methanol. (This is supposing there is a mass of methanol of 70kg inside the tank). We can find this by using the formula:
W=mg
so we can substitute the data the problem provided us with to get:

which yields:
W=686.7N
Next, we need to find the density of methanol, which can be found by using the following formula:

we know the volume of methanol is 75L, so we can convert that to
like this:

so we can now use the density formula to find our the methanol's density, so we get:



Next, we can us these values to find the specific gravity of methanol by using the formula:

when substituting the known values we get:

so:
S.G.=0.933
We can now find the force it takes to accelerate this tank linearly at 
F=ma

F=17.5N