\mathrm{If\; \Delta }\times 2.2+0.33\times \frac{3}{4}-\frac{1}{20}\times 0.55=0.99

. Let's double-check MathML formatting and tags: Raw unicode character for minus: - Raw unicode character for plus: + Raw unicode character for equals: = Raw unicode character for multiply: × (or ×) Let's construct the solution XML: 0.35

Correct Option: 0.35

To find the value of the unknown symbol \Delta, we can simplify the given mathematical expression step-by-step using basic arithmetic operations.

The given equation is:

\Delta \times 2.2+0.33\times \frac{3}{4}-\frac{1}{20}\times 0.55=0.99

Step 1: Simplify the second term.
Convert the fraction \frac{3}{4} to a decimal:
\frac{3}{4}=0.75
Now, multiply 0.33 by 0.75:
0.33\times 0.75=0.2475

Step 2: Simplify the third term.
Convert the fraction \frac{1}{20} to a decimal:
\frac{1}{20}=0.05
Now, multiply 0.05 by 0.55:
0.05\times 0.55=0.0275

Step 3: Substitute the calculated values back into the equation.
\Delta \times 2.2+0.2475-0.0275=0.99

Step 4: Combine the numerical constants on the left-hand side.
0.2475-0.0275=0.22
So, the equation simplifies to:
\Delta \times 2.2+0.22=0.99

Step 5: Solve for \Delta.
Subtract 0.22 from both sides of the equation:
\Delta \times 2.2=0.99-0.22
\Delta \times 2.2=0.77
Now, divide both sides by 2.2:
\Delta =\frac{0.77}{2.2}=0.35

Thus, the value of \Delta is 0.35.