1. The problem asks to solve an equation or integral using the method of change of variable (substitution). 2. To apply this method, identify a substitution variable $u$ that simplifies the expression. 3. Express the original variable(s) in terms of $u$ and rewrite the equation or integral. 4. Solve the transformed problem in terms of $u$. 5. Substitute back the original variable to get the final solution. Since the exact problem is not specified, here is a general example: **Example:** Solve the integral $$\int 2x \cos(x^2) \, dx$$ using substitution. **Step 1:** Let $u = x^2$. **Step 2:** Then, $du = 2x \, dx$. **Step 3:** Rewrite the integral in terms of $u$: $$\int 2x \cos(x^2) \, dx = \int \cos(u) \, du$$ **Step 4:** Integrate: $$\int \cos(u) \, du = \sin(u) + C$$ **Step 5:** Substitute back $u = x^2$: $$\sin(x^2) + C$$ This is the solution using the change of variable method.