solve function is used to numerically find the real roots of an
expression in a given
variable. It might have two or four arguments
solve('expression','variable')
solve('expression','variable','lower','upper')
When given two arguments, the roots will be searched in the range given by
Tools=>Options=>Roots(range). This is very important, if the root is outside that range it will NOT be found.
The precision of root finding depends on the option from the menu
Tools=>Options=>Decimal places 
Increase the number of decimal places for greater precision.HINT:
solve needs an expression and sometimes can fail. For instance, due to the way of calculating integrals in SMath (numerical solving) this can not be solved using
solve