By virtue of being presently unsolved, the remaining Millennium Prize Problems appear to be the most difficult.
source: [See related link below for the most difficult problems.
These problems have not been solved even by the most experienced mathmeticians today.
it was complicated
No. Tough can mean hard, but it can also mean strong. Tuff is a kind of volcanic rock.
hard, complicated, challenging, strenuous, arduous, onerous.
complex, purplexing, difficult, tough, cumbersomely, strenuously
A complex math problem is one that is hard to solve.
Unemployment means there are many job seekers in the economy but less jobs are available. Now a days in the world it is the hard and tough problem.
a hard nut, a hard nut to crack, a hard row to hoe, a tough cookie, a tough nut, a tough row to hoe, be as tough as old boots, tough as an old boot, tough as nails, tough cookie, tough customer
Because they emit radiation and is hard to dispose, It intoxicates the whole are its in.
Because they emit radiation and is hard to dispose, It intoxicates the whole are its in.
This is a simile comparing someone or something to nails. Nails are hard and tough, so this person or thing is being declared to be very hard and tough.
Hard and tough.
Anyone can if they work hard at it.
What hard ,tough and shiny that cover the crown?
the Hebrew word for complicated or hard (the opposite of easy) would be: kahshe and hard (the opposite of smooth) would be the same.
we can use tough instead of hard.
tough
tough,hard