How do you write 7.8 x 10squared in standard form

Table which ratio is equivalent to 3: 7? 6: 7 3: 21 24: 56 15: 30

1. 2. ∠b and ∠y are right angles. 3.? 4.? which two statements are missing in steps 3 and 4? ∠x ≅ ∠c △abc ~ △zyx by the sas similarity theorem. ∠b ≅ ∠y △abc ~ △zyx by the sas similarity theorem. = 2 △abc ~ △zyx by the sss similarity theorem. = 2 △abc ~ △zyx by the sss similarity theorem.

Which of these angles are complementary? a. 45o and 45o b. 63o and 117o c. 45o and 135o d. 90o and 45o