Answer:
Step-by-step explanation:
The formula for a triangle:
Base times height divided by 2
Equation Form:
b×h÷2
If I'm understanding the question correctly, 7+3=10. 10*8=80.
Check the picture below, that's the "inscribed angle theorem"
Answer:

Step-by-step explanation:
1) if according to the condition a₁=3 and r=2/3, then a₁₀ can be calculated as:
a₁₀=a₁*r⁹;
2) according to the rule above:
a₁₀=3*(2/3)⁹=512*3/(6561*3)=512/6561.