Answer:
Step-by-step explanation: 
1. The problem is telling us to start with the equation 5*0=0
2. Substitute. Any number plus its opposite is zero. Since the opposite of 10 is -10, 10+(-10)= 0:  5(10+-10)=0
3. 3 Use the distributive property. In other words multiply 5 by 10 and 5 by -10: 4·10+5·-10=0
4. Multiply. perform the first multiplication of step 4: 5·10=50, so: 50+4·-10=0
5. Subtract 50 from both sides. 50-50+5·-10=0-50; simplify the left side: 0+5·-10=0-40 
5·-10=0-50
6. Simplify to solve for 5·-10. Simplify the right side: 5·-10=-50
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Given.  5·0=0
Step 2 Substitute. Any number plus its opposite is zero.   5(10+-10)=0
Step 3 Use the distributive property.    5·10+5·-10=0
Step 4 Multiply. 40+4·-10=0
Step 5 Subtract 40 from both sides.    5·-10=0-50
Step 5 Simplify to solve for 4·-10.        5·-10=-50
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I Really hopes this helppps uu ! <3