Answer
$10$
Work Step by Step
$x^{2}-6x+3$ for $x=7$, first substitute 7 for each 'x' $$7^{2}-6\times7 +3$$ then, following order of operations, complete exponents first $$49-6\times7+3$$ next complete all multiplication and division in order left to right $$49-42+3$$, next addition and subtraction left to right $$7+3$$ $$=10$$