1. The problem is to substitute values directly into an expression involving $m_1$ without solving for $m_1$. 2. When substituting directly, you replace the variable $m_1$ with the given value or expression as is, without rearranging or isolating $m_1$. 3. For example, if the expression is $$F = m_1 \times a$$ and you are given $m_1 = 5$ and $a = 3$, then substituting directly gives: $$F = 5 \times 3$$ 4. This results in: $$F = 15$$ 5. The key rule is to perform substitution by replacing the variable with its value or expression directly, then simplify if needed, but do not manipulate the equation to solve for the variable. This approach is straightforward and useful when you only need to evaluate an expression for given values.