Answer:
There are 126 longs
Step-by-step explanation:
Let's represent the number of longs by l, number of flats by f and number of cubes by c.
We are told that there are 600 blocks in all.
This implies l + f + c = 600
We also know that there are 3 times as many longs as cubes: this mean
c = 3l
There are also 30 fewer flats than longs.
This mean f + 30 = l I.e f = l - 30
We now have 3 equations to solve simultaneously
l + f + c = 600 ...........(i)
c = 3l................(ii)
l -30 = f...............(iii)
We can substitute equations iii and ii into I
l + l - 30 + 3l = 600
5l - 30 = 600
5l = 630
l = 630/5 = 126.
